Ok, I have to eat crow on this one. Cracked # 3 piston which let the wrist pin come out and got the cylinder on both sides. I was a big advocate the LBZ piston but I'm thinking I may go back with LB7 pistons. I have seen all pistons crack but it seems the LB7 have a little better track record right now. No signs of any piston to valve issues or any signs of EGT issues, the piston flat cracked from cylinder pressure. The rest of the pistons look great but I'm sceptical of the LBZ piston now. No big timing in this tune up but I can't honestly say what happened.

Now I have to make a choice on what to do, do I build a .030 over race motor or do I put a stock motor back in and call it quits?

Sorry to here that man:o:

Well that sucks Ric. Hope you get her running soon. I'd think with all the modifications you've done to the truck you need to bore and build it again.

Thank-you for posting about the problem.

Thanks for posting, I know that's hard to do. I think there has been other failures that have been swept under the rug.

Too late for me, we do not have the time or money to switch so I will just try to keep things in check with the LBZ slugs.

Good news is that Casper's LLY slugs on the old engine look like new. No erosion or signs of heat.

As far as to whether or not to quit? Tough decision. When a hobby starts to interfere with your life instead of improving it, a wise man would change hobbys or downsize. Wish I had a cocaine addiction, it would be cheaper. :eek:

But in situations like this, I like to quote Forrest Gump:

I am not a smart man Jenny.

Believe it or not there are several people pushing me to not quit. I knew we were on the forefront of the LBZ HP level but it pi**es me off when I can't determine a root cause of failure.

I know some vendors don't get along but I was allowed to vent last night to several people who were very supportive such as Kyle (crankitupdiesel), Steve (TTS)(he got the brunt since he allows me to vent), Clint (ATS) and a few others. Tony has offered me his LLY short block to build and at this point my wife has said we will not let this beat us. The guys at Danville Performance have been awesome and we already have the motor out and partially disassembled.

At this point Steve (TTS), Clint (ATS), and Joe (PPE), Guy (SoCal Diesel) and many others have offered to supply part or whatever I need to rebuild it. It appears the block can be bored so I will consult with a few people and make a decision. This thing will be done in 2 weeks if everything falls into place. It will be the same group doing it a second time, Kyle, Myself, Mark, and DJ will turn it around as quick as humanly possible.

The plan as of right now is to put .030 LB7 modified pistons in the LBZ block provided the block can be salvaged.

Isn't there anyone who makes a BETTER piston than these stock ones?

These motors seem incredibly fragile for racing.

I like your spirit and drive!

Sorry to hear man :(

How were the pistons checked over before they went into the motor? Can a bad peice that had a flaw be rulled out? hate to think the slugs i got in my motor are weak......not that i like to think that there are a ton of crapy made ones floating around.....but I duno. 27k miles on mine.....havent realy flogged my truck though....

Sorry to hear man :(

How were the pistons checked over before they went into the motor? Can a bad peice that had a flaw be rulled out? hate to think the slugs i got in my motor are weak......not that i like to think that there are a ton of crapy made ones floating around.....but I duno. 27k miles on mine.....havent realy flogged my truck though....

That would make me feel uneasy for sure. I'd love to see someone use those Mahle forged steel pistons.....anyone wanna try:cool:

WOW: :eek:


You've got a keeper of a wife though. It would go like this for me...

ME - Well, I blew the d*mn engine again! I don't know if I'm gonna build a race engine now or go back to stock?
Her - You better know! You are going back to stock!! You are wasting soooo much money! Nag nag nag. Piss-n-moan, piss-n-moan. Yada yada yada. :lol: :D


Build it if you can, don't if you can't. Sounds like you need to plaster some BIG stickers on the truck if you build it back up though. ;) You're getting a lot of A-1 help from industry leaders sounds like to me. Good luck. I enjoy following your threads.

C-ya

There is someone talking to Mahle on my behalf to see if that is something we want to test. I like to be able to help you guys but I'm tired of taking one for the team!!!lol

The only way to check the pistons is to x-ray them.

That would make me feel uneasy for sure. I'd love to see someone use those Mahle forged steel pistons.....anyone wanna try:cool:

I'd love to. Do they have them for our engines?

I'd love to. Do they have them for our engines?

Wondered the same thing.....a thread just below this showed me these

http://www.all4engineers.com/index.php;sid=602720072461cfbb0a3a42401272502/site=a4e/lng=en/do=show/alloc=33/id=86

Mahle Monotherm's......looks like the Cat's Meow...

There is someone talking to Mahle on my behalf to see if that is something we want to test. I like to be able to help you guys but I'm tired of taking one for the team!!!lol

The only way to check the pistons is to x-ray them.

Cant you magnaflux em?

BTW....I actualy had a friend say he had a set of aluminum heads magnafluxed.....I asked him how exactly that worked ):h

So they were just visualy inspected?

Cant you magnaflux em?

BTW....I actualy had a friend say he had a set of aluminum heads magnafluxed.....I asked him how exactly that worked ):h

So they were just visualy inspected?

Sure you can, Phillip, you just have to use an "aluminum magnet!":rolleyes: :D

tazman did you have rods in this motor? did the rods hold up or were they damaged when the piston cracked?

I forgot Ric, were the pistons stock height or modded?

I've already started to warn the wife!

Rods held but the piston said I quit!

Well that sucks man, sorry to hear that. Hope you get it all fixed and figured out.

Rods held but the piston said I quit!

Yeah, and it was frigging getting it when it let go too! Nothing spectacular, just laided down and said no thanks, I'm good. We will get it fixed and keep going, it is part of the game we all love to play.

The pistons were stock. No mods or cuts of any kind. Well......1 of them is now modified!!:mad:

Are the 7 others going to be looked at to see if theyre hurt in anyway?

Yes, they will be examined to see if we can determine if there are any signs of fatigue or thermal damage.

We do appreciate you coming forward. I was getting ready to throw the kitchen sink at the 07 but I think I may wait and see what happens this summer. That will let some of us see whats working and whats not. The addition of the dual fuelers has sure brought out the weak points.

Yes, they will be examined to see if we can determine if there are any signs of fatigue or thermal damage.

We should all start a paypal account to throw some bucks in for ya....I'm sorry to hear about that man. Puts a pain in my wallet just thinking about that:( .

Ric

Sorry to here about the piston. That really sucks. I wish that on no buddy. Hope you get it back together in time.

I fell for you, man. So sorry to hear about the piston. It's more effort to build one of these motors than anyone will ever know. Until you actually do it, You'll never know. I appreciate you effort and give you a big "Boy Howdy" for all the greif. Don't give up though. Wish you the best.

BTW, I will be running LB7 cut pistons. We will find out soon if they will last. (It's all in the Name of science), Thank you Pat for putting this into perspective.

Well both heads are off and the thing looks like brand new minus the one broken piston.:mad: Looks like a bone stock motor does and no other damage other than the one cylinder(#3) with the broke piston. The LBZ slugs just can't take the pressure. It's really to bad because it was the coolest thing I have ever been apart of building and was stupid fast. We shall see how this all turns out but I know it will be stronger than before when it goes back together. We all apreciate the support.

Ric, thanks for sharing your experiences. This sucks for sure. Brings up a few questions though.

First, I am convinced that using an LBZ piston in stock form in a modded motor is not going to work. Too many cracked pistons. Funny how it happened last fall to Keith's motor and it was deemed the engine builders fault by many. Its pretty obvious IMO that these simply cannot handle the stresses. Next thing we need to know is how will the decompressed pistons hold up? So far, they seem to be working fine.

I do agree that using a LB7 piston is looking to be the best option right now. I am not sure if these are available in 030 oversize, but I know they are available in 020 and 040 oversize.

Guess that brings up the forged pistons again.... Ross pistons are being prepped right now for going in a twin turbo monster that looks to run right with Keith.

Thanks for the support from everyone. Tomac called me tonight to also share some of the pain. As far as money goes, I am not rich by any means but I believe in trying to do it right. I have enough help to get this thing rebuilt but I will admit I'm burnt out. Like I said before, I know we all disagree sometimes but I hope that no one builds a motor like this and has it happen to them no matter who it is. I do feel for Keith for having to deal with this also. A couple of friends used the LBZ pistons so I will feel like crap if their motor breaks. I'm not condeming anyones motor, maybe I just got a weak piston?

ATS, SoCal Diesel, PPE, TTS and Danville Performance have always supported me with this truck. My wife has been supper supportive. It's amazing how many quality people still exist when things happen. I've only known Tony and Tomac for a short time and Tony offered me his spare motor to help me out. If you guys show up at the dyno event this week or feel like giving some credit, drop Mark a PM and thank the guys at Danville Performance for all the help they have provided me with getting this going. The block will be ready for the machine shop tomorrow night and we will do this one more time.

I for one think what your doing is great. I'd like to help you out on the new build if you would accept it. The way I see it, it's not a donation. I'm paying you for doing some very expensive R&D work for me and everyone else in the Duramax performance community.:D Post or PM me your Paypal account if your interested.
Thanks,Bill

One curiosity remains.... I wonder why you are always in such a rush to get it back together? Is it your daily driver or are you just the type that doesn't want it to lag on? Just wondering? Perhaps a little more thought into selections could prove vital to longevity?

I'm not trying to critisize, just curious thats all.


C-ya

Good luck with the new motor tazman.:)
I bought my truck 4.5 months ago, and for a while I was wishing I would have bought an LBZ(6 speed, lower compression, higher factory horsepower, etc.) but now I am glad ive got an LLY.( I just hope its not an overheater:rolleyes:)

So LB7 pistons going back in then? Gonna cut them to decompress at all?

Rick
I knew you wouldn't quit.

Did you ever decide how to check the other seven pistons for cracks or problems? My advice is a dye penetrant and an ultraviolet light. This works well with airplane parts. It will show things you can not normally see.

Ric, sry to read about your issues that truck was a beast so watch at danville and was hoping to see some of your new additions. Hopefully you can get it all figured out and and press on.

is tony coming down this weekend so you can try to give his truck away again?

Smokeshow,

It might seem that I get things done in a hurry but it's because I don't like having a new truck down and I'm one of those guys that will work 48hours straight to do it right. Once I start, I don't like getting side tracked and because I tripple check everything, I tend to just stay focused and keep working. That's just how I am! Anyone that has seen my truck knows I'm very particular about everything.

LB7 pistons will be going back in the motor. We decided to go .040 oversized and the compression ratio is yet to be determined. I refuse to have a trailer truck so I will probably stay around 16.3-1 or so. I do trailer it if we are going a long way away but I like driving the thing.

The original pistons will be examined and I would prefer to have them x-rayed but I have not decided exactly needs to be done. The pistons will be packaged with no removal of any material or prior cleaning to give the best representation of what the engine was actually doing. I'm open to suggestions as to where we can get these checked.

I did have reservations about posting this but I felt it was the right thing to do. I do have a paypal account but at this point we are finacially preparred to handle the issue I think and I hope that no one else has to put out the money to repair anything like this. It appears that we have tested the LBZ far more than anyone else at this point and I think we are building the final product this time.

Again, I appreciate all the support, it means a lot. The guys that are really get screwed on this deal are the guys that have to help me build it again. Poor Kyle has to drive from Ohio and stay the night and Jason has to drive from Arkansa to help. We have a system set up that works pretty good and everyone knows exactly what has to be done.

Wow! :eek: Simply amazing and very inspirational Ric.

Good luck and take care.

I eagerly await the autopsy of the other slugs. That may help show if you got another junk slug(and one can start to extrapolate thereis a serious quality controll issue out there) or if the design sucks.

Thanks for helping us all learn from this :)

I hope it all works out for you Ric. I feel your pain, my puller has been dead for about 7 months now while I collect all the parts for fix/improve it. All the while still making payments. Please keep us posted, the info you give is very informative.

If you've already answered this I apologize, but which cylinder did each crack occur in? 3 &/or 5?

#3

Yeah, we enjoy driving it around as much as the weather permits us to. Ric is just like Larry and I as we don't like down time as it costs more in the the long run. Jason and Kyle are great to work with and look forward to doing it agian.

Sorry about the tough luck Ric! Owning a Duramax is kinda like getting married, you invest a bunch of money praying that it all works out in the end!:D Good luck with the rebuild.

curious what your using for headgaskets with the .040 over pistons. Sounds like a great plan on the LB7 pistons Ric. Good luck with it all. Kudo's to those helping get this thing up and running again.

that bites hardcore. At least you got the guys at Danville to help get things movin

sad to hear ric, as you may know i had a cracked piston just a few weeks ago on the lbz, running around the 580-640hp, there was no signs of high egts, or anyother cause... to add salt to injury

we have a few others up here running the gt42, dual fuelers, and big programing650 to 750hp.... i think the thing we are most worried about is the cracked piston... looking to be the real weak spot in these things

hope she works out for you as you look to have a lbz money pit as well

i wish i would of kepted the lb7...

Stock head gaskets have a bore of 4.100" so it will be close with them but they will be fine. Have some new ones being made but not sure if they will be ready in time.

WOW...just seen this thread. Thanks for the info. Good luck on the build.

Hopefully the stock gaskets will be close but I'm looking at another option right now. This will be a interesting build but I will not short cut it. I could probably use the overbore gasket for the LB7 and be ok.

Rick,

After all the heat you took in the bent rod thread, to come back in here and share this info with the community.

This speaks volumes about your character.

You're one hell of a guy! :ro)

FYI, the new head gaskets from GM have a bore of 4.145-4.155

does anyone make a aftermarket piston for the d/max its a shame all the money spent on these and no big piston company will come up with it.gas turbo cars make alot of pressure with no problems?why not the d/max.
sorry to hear about it.

does anyone make a aftermarket piston for the d/max its a shame all the money spent on these and no big piston company will come up with it.gas turbo cars make alot of pressure with no problems?why not the d/max.
sorry to hear about it.

I'm not expert, but from what I gather the geometry in the Duramax motors has dictated some of the piston design. The angle of the bores relative to centerline, length of rod, pin height in piston, etc. have posed an issue for aftermarket piston designers. That combines with the wear characteristics of diesel motors dictates certain materials be used in the ring area to prevent wear.

The Cummins has some beefy aftermarket pistons designed for it, but many of those designs don't easy translate over to our V8. Basically a new design as well as rod (and maybe even crank) changes look to be needed in order to make the current technology work, which is BIG $$$. Hopefully someone who has more knowledge than most of us on here will have an idea to work around the current metallergic and goemetric issues, but until then all we can do is hope.

And I can say with almost certainty that there are big name companies (and maybe even small ones) that are working on the Duramax "Piston Issue", they just haven't found the right combo yet (or not yet made it public).

quote

As far as to whether or not to quit? Tough decision. When a hobby starts to interfere with your life instead of improving it, a wise man would change hobbys or downsize. Wish I had a cocaine addiction, it would be cheaper. :eek:


Well said!!

never quit man, a cocaine addiction???^^?, fast cars are way better than drugs dude!! build that beast

Man that suck, i feel your pain, i will be buildin mine, but i dont have the money or time at the moment, so i am just droppin in another in the mean time. I think my LB7 slugs are ok, i just got a lemon, so i will probably stick with them. But its gonna be a long process, if you have any tips or suggestion i would appreciate it if you would let me know. But good luck, we are all behind you. Or if anybody else has any suggestions, please pm me, i really have no idea what i am going to be doing, lol.

Good Luck Taz,

You have a great group supporting you, you'll get it done for sure !!!!

Thanks for sharing your experience with the LBZ.

;)

Out of all of the recent LBZ piston failures, have any of you guys have your pistons de-compressed?

One other question, is the wrist pin the same size as an LB7 pin? I know there is a brass or bronze bushing pressed into the piston, and if the wrist pin is the same diameter, that means the the hole in the piston for the bushing to fit is much larger than the wrist pin hole in an LB7 or LLY. This bushing is doing nothing for strength, in fact if it's just a press fit in the piston it's actually making the piston itself weaker, because there is less material holding the piston together.

The LBZ piston pin area is longer than the LB7/LLY with more material added aroung the wrist pin hole area. The bushing is then machined into the beefer area. So yes, some more material is removed but there has also been more added in the base part both in length and diameter. This past week there has been both an LB7/LLY piston fail and a couple LBZ ones fail. I think we are just reaching beyond the limits of either piston at this time. Last year 600 - 700 HP and things were holding fine, this year 900 - 1000 Hp and things are starting to let go again. While I wish there was a better solution now there just isn't and it appears to be a crap shoot with the quality control on the pistons. We've got some well over 700 RwHp and 14,000 miles holding great then the next guys come apart after a couple hundred miles.

... We've got some well over 700 RwHp and 14,000 miles ...

There has been more than a "couple" of LBZ piston failures.

Not my trucks, so it's up to the owners to say.

The definition of insanity is doing the same thing again and again, while expecting different results.

BTW, all 8 LLY pistons in Casper's original OEM engine look brand new.

At this point, I would not suggest anyone spend the extra money to get LBZ pistons if they already have LB7 or LLY slugs around.

If anyone would mind to share....

How many LBZ piston failures have occured now?

Also, whats about the most HP you need to run through it to keep it safe?

If anyone would mind to share....

How many LBZ piston failures have occured now?

Also, whats about the most HP you need to run through it to keep it safe?

Looks like there are 2 more in here :(

http://www.dieselplace.com/forum/showthread.php?t=150191

One other question, is the wrist pin the same size as an LB7 pin? I know there is a brass or bronze bushing pressed into the piston, and if the wrist pin is the same diameter, that means the the hole in the piston for the bushing to fit is much larger than the wrist pin hole in an LB7 or LLY. This bushing is doing nothing for strength, in fact if it's just a press fit in the piston it's actually making the piston itself weaker, because there is less material holding the piston together.

The LBZ piston has added beef around the wrist pin. But it is all below the the center line of the wristpin bore. How much does it really help. Not much IMHO. The problem is the wrist pin bore in the piston is a good deal bigger. So is the oil cooling gallery. To get all this stuff in things had to be a lot closer. The distance from the major diameter of the piston bowl to the top of the oil gallery is much smaller on the LBZ piston than the LB7/LLY piston. I brought this up months ago and good flamed for it.

That being said I think the LB7/LLY piston is marginlly stronger but not a whole lot. I really think most of the trouble is the thinking on how we should make power. If we had beefier piston and we tried to make big power at 2500 to 2800 rpm like is being tried now how long till the bottom end is laying on the ground!:D Stand back and look at what tractor pulling diesels have done. They do not try to make power 3000 rpm and below. Why? It breaks stuff! They set their engines up to get them as close to 5252 as they can. Why? They can make power and live! Why? Because it takes a lot torque (ie. cylinder pressure) to make the same power at 4500 rpm than it does at 2500 rpm. Simple non fuzzy math!:) The trouble is it takes the right cam, comp. ratio, turbo, and valvetrain to work up that high. To keep these things alive need to limit torque and focus on horsepower.

Go talk to EEP, Scheids, Lusticks, and or any other real diesel perfomance shop. See what they say.

It doesn't get any better than this explanation. Thanks Johnboy for the great info. High Cylinder pressure at low rpm's=broken ****!

Looks like there are 2 more in here :(

http://www.dieselplace.com/forum/showthread.php?t=150191


Are all 3 running dual fuelers? (Taz and the 2 above)

We feel the pain of the Dmax community - Importkilla's truck has been down since October. May even be going back to a stock turbo setup:mad: .

[quote= We've got some well over 700 RwHp and 14,000 miles holding great then the next guys come apart after a couple hundred miles.[/quote]


This I'm guessing is probably related to the style of driving these trucks are under. Mine lasted 10-12000 with 526RwHp, but anyone who knows me that was probably borrowed time. I'm sure Tazman is the same way. If I drove my truck to work or church it would of lasted longer. But when you drive to pretty much every pull, then pull and make the drive home racing everything in sight thats what is hard on these trucks. If all my truck did was pull it would last me a lifetime. The moral of this is if you bought this truck to beat the piss out of it don't modify past stock turbo or you will be in the same sinking boat we are in.... It will drag your bank account down with it.

Now lets see how many people I pissed off with that post.

If the style of driving alone is the issue then I'll break all of mine.):h

I run my trucks harder then most, day in and day out. I'll haul max GVWR one way, and race every truck and car I can find on the way back. Some last and some don't. There has to be a reason buried in there somewhere. Maybe an overzealous injector combined with more piston protrusion?

Importkiller

Nick drives his pretty much like he stole it and that sounds the same as you do, so I do not think in his case driving style is playing a part in it as his is beat hard just about every day and the power level has never been turned down event though he could. I am beginning to think there is more going on with the quality control of these pistons from the factory. I would like to get some of the failed pistons to section and see if they are not keeping things in the same place on all the pistons. So now the question becomes how do you know what you've got when you buy them before installation. I've attached a photo of a couple pistons sectioned with the wrist pin through both so you can see the differences in them. The dimensional changes around the oil galley to the dome are all pretty close between the 2 styles of pistons.
While I disagree with Johnboy about the strength issue of the added material and its placement we both agree that they are both failing and we need something better. I believe there is something more going on and we just have not found it yet. This is causing the premature failures to occur for some and not for others.

It's pretty easy to test the piston strengths for someone with numerous engineering resources. If someone wants me to draw up blueprints for the fixture required, let me know, but destructive testing is not exactly rocket science.

For us hobbiest racers, we kind of have to go by published results. Which indicate the LBZ pistons are showing a problem early than LLY/LB7 pistons.

I would like to get some of the failed pistons to section and see if they are not keeping things in the same place on all the pistons.
This sounds like a good idea, if you are interested in my LB7 piston as well, i can probably ship it to you some time next week if you pm me your adress. Common sense seems to dictate that this is a qc problem, i mean if it was to much power, wouldnt we see multiple pistons failing at the same time. Much in the same way that we dont generaly see one bent rod in a high power situation?

... I really think most of the trouble is the thinking on how we should make power. If we had beefier piston and we tried to make big power at 2500 to 2800 rpm like is being tried now how long till the bottom end is laying on the ground!:D Stand back and look at what tractor pulling diesels have done. They do not try to make power 3000 rpm and below. Why? It breaks stuff! They set their engines up to get them as close to 5252 as they can. Why? They can make power and live! Why? Because it takes a lot torque (ie. cylinder pressure) to make the same power at 4500 rpm than it does at 2500 rpm. Simple non fuzzy math!:) The trouble is it takes the right cam, comp. ratio, turbo, and valvetrain to work up that high. To keep these things alive need to limit torque and focus on horsepower.

Go talk to EEP, Scheids, Lusticks, and or any other real diesel perfomance shop. See what they say.


Amen. :cool:

Sure you can, Phillip, you just have to use an "aluminum magnet!":rolleyes: :D


Not to mention that only checks for surface cracks.

What kind of Hp and TQ #'s are theses piston failing at? I just ordered my PPe tuner but now don't know if I want to put it in the truck.

I beleive Fred wasn't running dual pumps when his failed. Myne was also acting up prior to the dual pumps. So these are failing at a relativley low hp number 550-600 i would say. Cutting them down may make them last, but im planning on a different route to be sure. At this time i would not build with the LBZ pistons until we get this figured out.

This sounds like a good idea, if you are interested in my LB7 piston as well, i can probably ship it to you some time next week if you pm me your adress. Common sense seems to dictate that this is a qc problem, i mean if it was to much power, wouldnt we see multiple pistons failing at the same time. Much in the same way that we dont generaly see one bent rod in a high power situation?

I agree, but not looking into and understanding why they have failed event if it's determined to be a QC problem leaves us open for more failures in the future. My hope is we can learn some way to check the piston prior to installation without destroying them to make sure they are good to go. PM sent for the LB7 failed piston too.

That being said I think the LB7/LLY piston is marginlly stronger but not a whole lot. I really think most of the trouble is the thinking on how we should make power. If we had beefier piston and we tried to make big power at 2500 to 2800 rpm like is being tried now how long till the bottom end is laying on the ground!:D Stand back and look at what tractor pulling diesels have done. They do not try to make power 3000 rpm and below. Why? It breaks stuff! They set their engines up to get them as close to 5252 as they can. Why? They can make power and live! Why? Because it takes a lot less torque (ie. cylinder pressure) to make the same power at 4500 rpm than it does at 2500 rpm. Simple non fuzzy math!:) The trouble is it takes the right cam, comp. ratio, turbo, and valvetrain to work up that high. To keep these things alive need to limit torque and focus on horsepower.

Go talk to EEP, Scheids, Lusticks, and or any other real diesel perfomance shop. See what they say.

Forgot a word and to much time had passed to edit it. Should be more clear now.

Is it me or does the lip on the LBZ piston look choked down?

Looks like the distance between the bowl and oil gallery on the LB7 is quite a bit thicker than the LBZ. Also draw a line vertically at the deepest point in the bowl and look at the thickness difference there. IMO the LB7 pistons are going to be a bit stronger. It was said that there was more material below the wrist pin in the LBZ piston...I don't see it. That bushing is only taking strength away from the piston.

Could you use LB7 pistons with Lbz rods? Oh and tlee05 its not just you it does look as if the lip is choked down to me also

:exactly: Looks like the distance between the bowl and oil gallery on the LB7 is quite a bit thicker than the LBZ. Also draw a line vertically at the deepest point in the bowl and look at the thickness difference there. IMO the LB7 pistons are going to be a bit stronger. It was said that there was more material below the wrist pin in the LBZ piston...I don't see it. That bushing is only taking strength away from the piston.

You all need to understand that the bowl area in the LBZ is bigger than the LB7/LLY. So if your looking at lowering the compression by opening the bowl up on a LB7/LLY you are right back where the LBZ piston is to start with. The picture can deceive you some on the dimensions so here they are from the pistons in the picture.

Thickness from the center of the bowl to the bottom of the piston (thickness) LB7 = .414" LBZ = .407", .007" difference about as thick as a human hair.

Distance from oil galley to the bowl where the marks in the pictures are
LB7 = .290" LBZ = .240", .05" difference

Diameter of the bowl at the point where the oil galley measurement is from, this is the widest part of the bowl.
LB7 = 2.46" LBZ = 2.52" , .06" difference

What the pictures do not show is the amount of material around the pin area and the longer length of the pin area on the LBZ piston. The LBZ surface area contact with the pin is also much greater than the LB7. An LB7 pin is 3.039" long with a gap in the center of the piston of 1.360" which leaves you with 1.679" of pin length in contact with the piston. The LBZ on the other hand has a pin length of 3.157" and a gap in the center of the piston of 1.180" which leaves 1.977" of pin in contact with the piston. This give the LBZ more support by .298" of contact surface with the piston, this will spread the load out over a greater area making it much stronger. This is why I prefer the LBZ piston.

Now if you are to lower the compression by opening the bowl area of an LB7 piston so that it has the same compression ratio as the LBZ piston you would end up with the oil galley distance to bowl of LB7 = .260" LBZ = .240". So as you can see pretty close to the same on both.

What we do not know is where is the crack starting from. I have a piston coming to me from a member here that has a crack just starting and has not yet cracked all the way. Once it gets here we can see if it is down to the pin area or just on the top of the piston. If the crack does not start in the pin area then we know that its the end result not the starting point in the LBZ piston.

Could you use LB7 pistons with Lbz rods? Oh and tlee05 its not just you it does look as if the lip is choked down to me also

You can use any piston on any rod in the duramax. You just need to use the proper pin to go with the piston.

The LBZ piston has added beef around the wrist pin. But it is all below the the center line of the wristpin bore.


John this is not true, there is more above and below the pin. Look at my previous post where I give the piston pin gap area as that is above the centerline of the pin. Also the contact area between the pin and piston is longer which also is above the centerline.

0.007" for a human hair? Must be a Samoan pubic hair! :D

A human hair is .003" to .0015" depending on the color and type.

0.007" for a human hair? Must be a Samoan pubic hair! :D

Do I dare ask how you know this? :eek:

0.007" for a human hair? Must be a Samoan pubic hair! :D

A human hair is .003" to .0015" depending on the color and type.

Guess mine are just a bit bigger than some. :eek:

Do I dare ask how you know this? :eek:

Well when I tell someone they're a c### hair off, I need a reference! :D

When I was a machinist, I had a 3x5 card in my toolbox that had a hair taped to it: (1) Imperial C### Hair, traceable to NIST. Calibrate on use.

;)

Guess mine are just a bit bigger than some. :eek:

Hell Steve, you're BALD!!! :D

Hope you guys find the root problem with these pistons since I sold my 02 yesterday and bought my lbz 3 hours after that. Was wanting to mod after I get some miles(McRat Efi) but might hold off until some info evolves.

Ha ha Pat I almost fell off my chair laughing when I read your last posts. :)



Taz sorry to hear of your problems dude. Thanks for sharing with the rest of us. I hope you get it figured out.

So far Wendy has been trouble free, and has been running tuning from 500mi up. It always runs the biggest tune we have available daily.

But there are no guarantees in hot-rodding. Some LBZ's have blown up stock, mostly from glowplug problems.

LLY's and LB7's are no different, and have blown up stock, as well as with big tuning. But the history has been generally good with tune-only.

I think I have about 55 LBZ's running the "Wendy" tune so far. The one's that are tune-only are so far good to the best of knowledge.

I do tell everyone that increasing the output of an engine reduces it's life. Be it a Honda, Corvette, or a Duramax.

Rick is running on the "bleeding edge" of LBZ performance. For these apps, I'm not convinced LBZ pistons are the best choice. But there is LBZ pistons in Casper's new engine. This gives me more incentive to come up with ways to be more gentle on the engine when going for big power output.

Just my opinion, but there is more meat over the pin on the LB7 and the oil passage is a bit lower/thinner. True, there is more material in the LBZ over all, but I am not convinced it is all in the right place.

Again, just my opinion.

I selected the LB7s for my build because of the oil passage position. It worked out well with the mods I had done to the bowl. We will see how it pans out.

For inspection, we could use Xray or radiography to check for flaw in new pistons.

But there is LBZ pistons in Casper's new engine. This gives me more incentive to come up with ways to be more gentle on the engine when going for big power output.

Or live in the Dog House forever :eek: Just kidding, if he blows he blows and we will rebuilt him again :hug:

We have discussed the material over the centerline the wrist pin in the other thread. I disagree with you Steve. Kind of pointless to argue about it now. The wrist pin is longer which is good but the bushing negates any gains from its added support IMHO. I believe as I have for a long time the oil gallery and its positioning in relation to the bowl is the main issue. Is it really worth spatting about know? No. The LBZ piston I bought and cut in two I no longer have. As I sent the halves out for some other opinions that are more experienced with diesels then me. Results where interesting. Also I was surprised by who had already surveyed the situation.
What they told me?

The truth is we need to rethink how we are making power. I said this earlier in this thread and in the other piston thread.
Look at the failures in order. Turn up the power and what goes first? The rods bend. You get better rods and the pistons fail. You get better pistons and what goes wrong next? The crank? The heads? The whole bottomend laying on the ground? When will it end? Truth is it will not as long we keep trying to make power the we are. This is something I have learned from diesel sled pulling. We are not the only ones to run into this before. We need to learn form those that have been here before. As long as we try to keeping big power below 3000rpm we will have trouble. There comes a point in time when you must decide which side of the fence you are on. Go big or stay small? When try to do both or stay in the middle standing over the fence your balls get busted. IMHO many are straddling the fence right know.

What does it take to make horsepower? Torque and RPM. The answer could very well be in the formula itself (Torque x RPM)/ 5252 = Horsepower. Simple nonfuzzy math. Let me use 1000hp as an easy example. At 2500rpm you need 2101lbsft of torque. Will that break stuff? Hell yeah! Truth be told, Torque (cylinder pressure) is the killer here. Very few engines will live for any length of time at that torque level. Now lets try 1000hp at 5000rpm. It takes 1050.5lbsft of torque. Will are engines live at that torque output? Many have been running at that torque level for a good while now. What about that rpm can we live there? Are chances of making that work are far better than at 2500rpm and 2000lbsft of torque. Can we really get there now? No. The LB7/LLY ECM will prevents this. Truth is over 4500rpm I have had issues with the reliability of the fueling controls. I do not think the ECM ,FICM can react fast enough IMHO. The LBZ electronics have the potential to get there and past. We are not capable of using them to their potential yet.

My focus the last four months has been to figure out how to make my truck work at 4000rpm. I can fuel relievable to there. Figuring out what else is needed is the really difficult part. Can I make it work? I do not know. There is only expensive way to find out. One thing that may really help is my trans. I have serious doubts that the Allison will live long at the RPM I want to run. The real trick is getting the cam, turbo, valve train to work together at 4000rpm.

To those that have come forward with the truth about you engine failures Thank You! It sickens me to read some of these posts. I feel very bad for you. All this carnage makes me wonder is it really worth me pressing on.

Some LBZ's have blown up stock, mostly from glowplug problems.


You know what is ironic? Even though I am not the fondest of LBZ pistons. There are 8 in my drive way right now. I am depending on them to tow the big truck!:eek: LOL! Better leave hitch the bed of the big truck.;)

I agree John, and have been working in that direction myself. Valve train is critical to keeping it alive at speed and as of right now is the biggest stumbling block to keeping it together. At least for me.

I feel your pain Taz. With the $$ in these engines, it is hard to keep the faith when things start going bad.

I have been getting a lot of calls from people in relation to what my intentions are to repair the engine. We have decided to use the Mahle LB7 pistons and have them coated. We were considering using a forged piston but it just wasn't a viable option at this point.

I feel the risk with the LB7 pistons is less than the LBZ but both can be broken with enough cylinder pressure. My truck should be ready to go in about 2 weeks so we'll see how it works.

Is it possible that the LBZ pistons had the material added to make up for being made out of a "lesser" quality material. Has anyone actually compared the material these pistons are made from to the LB7 pistons??

i agree 100% Johnboy

I have been getting a lot of calls from people in relation to what my intentions are to repair the engine. We have decided to use the Mahle LB7 pistons and have them coated. We were considering using a forged piston but it just wasn't a viable option at this point.

I feel the risk with the LB7 pistons is less than the LBZ but both can be broken with enough cylinder pressure. My truck should be ready to go in about 2 weeks so we'll see how it works.

Were you monitoring cylinder psi on this before it broke? Drive psi? Egt's? Rail psi? Are your injectors good?

I disagree with you Steve. Kind of pointless to argue about it now. The wrist pin is longer which is good but the bushing negates any gains from its added support IMHO. I believe as I have for a long time the oil gallery and its positioning in relation to the bowl is the main issue.

We all will never agree until we solve the problem and at that point we will know the answer, what ever it is it is. Johnboy and I have discussed it at length and we disagree on what the effects of the bushing will be but the bottom line is we are both trying to find and resolve the problem. Getting more pistons for inspection may lead us to the answer and the ones with cracks just starting will help alot. If they are starting from the wrist pin area, the oil galley or the bowl area heads us in the right direction.

Highest EGT was 1625F and the injectors are fine. They were new also.

Looks like the distance between the bowl and oil gallery on the LB7 is quite a bit thicker than the LBZ. Also draw a line vertically at the deepest point in the bowl and look at the thickness difference there. IMO the LB7 pistons are going to be a bit stronger. It was said that there was more material below the wrist pin in the LBZ piston...I don't see it. That bushing is only taking strength away from the piston.

This is what me and a few others have said all along. I agree with you.

It seems that all the machinist and engineers are siding with the LB7.

Tazman,

Thanks for sharing your findings. I realize this is getting mighty expensive for you and wish you the best of luck getting it back up to speed.

Thanks again for keeping us informed.

It seems that all the machinist and engineers are siding with the LB7.

Not all. If you look at the picture I have attached you are seeing a failed LB7 piston. This is out of a truck running about 400 - 425 RwHp. As you can see it did not crack completely across both sides of the piston so it gives us some insight as to what might be happening. It appears to have cracked across the top of the piston first and headed downward into the bowl and into the pin area. I had to cut one side then break it free from the side with the crack already in it.

Interesting! Do you have a top veiw? From that veiw it is hard to tell if the crack is parallel to the wrist pin. That one really looks like it started from the top and headed down. Any pitting or valve contact marks on the top?

By the way thanks for sharing.

Not all. If you look at the picture I have attached you are seeing a failed LB7 piston. This is out of a truck running about 400 - 425 RwHp. As you can see it did not crack completely across both sides of the piston so it gives us some insight as to what might be happening. It appears to have cracked across the top of the piston first and headed downward into the bowl and into the pin area. I had to cut one side then break it free from the side with the crack already in it.


Anymore pics? Thanks for sharing that, interesting indeed.

Interesting! Do you have a top veiw? From that veiw it is hard to tell if the crack is parallel to the wrist pin. That one really looks like it started from the top and headed down. Any pitting or valve contact marks on the top?

By the way thanks for sharing.


Pretty close to parallel to the wrist pin for as long as it went(95%). No pitting on top except around the area where it melted the metal out, none on the top of the piston or the bowl top radius. Motor was rebuilt and used the same injectors but I do not have a complete history on it. If the others coming in all are the same then some conclusions can be draw between them all. I have a pretty good idea of what I think is going on from the damaged pistons I've gotten so far.

Here is yet again another cracked LB7 piston. Crack is like the others in that it appears to have started on the top and worked its way down. Crack runs pretty close to parallel to the pin (95%). This one was crack near the full piston width as I didn't have to cut much at all. I've got more but have not cut them all up yet.

So you still think a LB7 piston is the answer?

When I get the LBZ pistons if the cracks are the same then there has got to be something common between them.

Here is yet again another cracked LB7 piston. Crack is like the others in that it appears to have started on the top and worked its way down. Crack runs pretty close to parallel to the pin (95%). This one was crack near the full piston width as I didn't have to cut much at all. I've got more but have not cut them all up yet.

So you still think a LB7 piston is the answer?

When I get the LBZ pistons if the cracks are the same then there has got to be something common between them.


Why is the flame pattern so far to the outside of the piston??
Is this normal, or was this engine running to much timing?

Even a 100% stock tuning truck puts that star pattern on top of the piston.

Yes, there has been LB7/LLY cracked pistons. Mostly through 2 events:

Massive drug amounts

Stuck injectors

But the concern raised about the LBZ pistons is that there are relatively few hotrodded LBZ's out there yet, and we have heard of 3 failures PUBLICALLY in a short time.

Steve is claiming they are just as common on LB7/LLY. Perhaps. That would mean hundreds of cracked pistons on this board alone to maintain the ratio. This is where the secret squirrel has rabies. If in fact there are hundreds of cracked pistons among our members, keeping them a secret is working against us.

And if most the cracked pistons are secrets, it would not be a stretch of the imagination to assume many LBZ piston problems are secret as well. This would really push up the failure ratio.

If the LBZ piston is indeed stronger, let's see it. Failure rate data is not indicating it.

Is it possible that the LBZ pistons had the material added to make up for being made out of a "lesser" quality material. Has anyone actually compared the material these pistons are made from to the LB7 pistons??

I did some metallography on both and visually there is zero difference between the two, in terms of microstructure.

Now if either one has some pixie dust thrown in the alloy, I wouldn't be able to see it, so I can only vouch for the alloys being "extremely similar" in terms of grain size and morphology.

I kinda believe that both pistons are marginal at these HP levels and the true "fix" is something completely different....JMO though.

I really have to wonder how many of these failures are the interaction of tuning, individual injectors, and individual pistons. I believe it's possible that one goofy injector (hosed up spray pattern, leaking, sticking, etc.) could be a bigger contributor than expected.

We're all focusing on the piston (with good reason) but we shouldn't forget the other portions of the equation.

...We're all focusing on the piston (with good reason) but we shouldn't forget the other portions of the equation.

Agreed. There is something else going on. We know that with pure force alone, the rod bends first. It is a combination of factors that crack a piston.

But the idea that an LBZ piston will take more abuse seems to be false at this point. It looks like a tie at best, but most likely slightly weaker.

is it always happening on the same cylinders?or it does not matter the piston are failing every hole?

is it always happening on the same cylinders?or it does not matter the piston are failing every hole?

There's been a poll started for those that have had a cracked piston, to state which one(s) cracked. This is to try and see if there is a trend. ;)

Well just to dis spell the rumor mill the pistons I post had no drugs run on them and had no injector failures. The failures are a lot more common than one would like to think when you start digging into it. It's just High Hp builds that get all the attention here on the board. There is a lot more work that we have done into this than anyone here knows about as it's been an ongoing problem for over 3 years. If your looking for data it's posted in the pictures I have supplied but for some not event that is good enough. When the piston manufacture came out an said the LBZ piston is stronger than the LB7/LLY piston they produce, these same rumor mill people said it's not true.

Let's look at the data from LBZ pistons that did not have valves hitting them due to mis assembly:

Tyson cracked 2 LBZ pistons but also has 8 bent rods in the motor
Tazman cracked a LBZ piston but also had bent 8 rods prior to the piston failure.
Fred W. failed one LBZ piston
1FastMax failed one LB7 piston

All motors have been run well over 600 Hp with no drugs and plenty of stress placed on the piston prior to failure. All have agreed to sent the pistons in so we can inspect them.

There are plenty of LB7/LLY piston failures without drugs and without injector failures and guess what, the ones that have sent pistons to me have all had cracks that appear to have started on the top of the piston not around the oil galley or in the pin area. Surface hardness testing has shown no signs of a heat problem with the material. Now some LBZ's are doing the same thing. Until we get the pistons here and cut them apart to see we cannot say for sure what is happening but open your eyes and look at the writing on the wall here. There is most likely something common going on between both piston designs as they are both failing at raised Hp levels

Tyson cracked 2 LBZ pistons but also has 8 bent rods in the motor
Tazman cracked a LBZ piston but also had bent 8 rods prior to the piston failure.
Fred W. failed one LBZ piston
1FastMax failed one LB7 piston

Are you sure those are the only ones?

What oil were you running Tazman?

Are you sure those are the only ones?

I am sure there are plenty more out there in all piston designs but these are the ones reported here on the board. I've heard of a couple more but haven't been able to get the necessary information to confirm what they are for sure and get pistons to check out.

Well just to dis spell the rumor mill the pistons I post had no drugs run on them and had no injector failures. The failures are a lot more common than one would like to think when you start digging into it. It's just High Hp builds that get all the attention here on the board. There is a lot more work that we have done into this than anyone here knows about as it's been an ongoing problem for over 3 years. If your looking for data it's posted in the pictures I have supplied but for some not event that is good enough. When the piston manufacture came out an said the LBZ piston is stronger than the LB7/LLY piston they produce, these same rumor mill people said it's not true.

Let's look at the data from LBZ pistons that did not have valves hitting them due to mis assembly:

Tyson cracked 2 LBZ pistons but also has 8 bent rods in the motor
Tazman cracked a LBZ piston but also had bent 8 rods prior to the piston failure.
Fred W. failed one LBZ piston
1FastMax failed one LB7 piston

All motors have been run well over 600 Hp with no drugs and plenty of stress placed on the piston prior to failure. All have agreed to sent the pistons in so we can inspect them.

There are plenty of LB7/LLY piston failures without drugs and without injector failures and guess what, the ones that have sent pistons to me have all had cracks that appear to have started on the top of the piston not around the oil galley or in the pin area. Surface hardness testing has shown no signs of a heat problem with the material. Now some LBZ's are doing the same thing. Until we get the pistons here and cut them apart to see we cannot say for sure what is happening but open your eyes and look at the writing on the wall here. There is most likely something common going on between both piston designs as they are both failing at raised Hp levels


So you've been cutting apart pistons for 3 years and your solution is? LBZ Pistons?

It is a combination of factors that crack a piston.


Thats what I was getting at earlier, you said the star pattern was to the outside of the piston even with stock tuning, but wouldnt advancing the timing move the star pattern even further to the outside?? Which in turn would not only increase peak cylinder pressure, but it would also place the load further out on the piston....Right? I geuss my point is it seems like it is using the wrist pin as a fulcrum point, so placing the load farther out increases the leveredge it has on the piston. I know you have to advance the timing to make power, but maybe were are going to have to sacrifice a little power for longevity. JMO.

But the idea that an LBZ piston will take more abuse seems to be false at this point. It looks like a tie at best, but most likely slightly weaker.


If this is true, why did you use LBZ pistons in casper's new engine?

If this is true, why did you use LBZ pistons in casper's new engine?

Because we started on the engine months ago, before Casper lost compression.

At the time, the general consensus was LBZ pistons were stronger, and on paper, it seemed correct.

Problem is, reality is getting in the way of theory. If I had the money and time, I would switch back to LLY pistons. But I have neither right now.

I was originally going to go with forged Ross pistons, but after talking with some folk who actually built engines using them, they did not recommend them.

After seeing that Casper's original pistons looked like new, I perhaps made a wrong decision. Not a first for me, I've made LOTS of mistakes! :D

Here is yet again another cracked LB7 piston. Crack is like the others in that it appears to have started on the top and worked its way down. Crack runs pretty close to parallel to the pin (95%). This one was crack near the full piston width as I didn't have to cut much at all. I've got more but have not cut them all up yet.

So you still think a LB7 piston is the answer?

When I get the LBZ pistons if the cracks are the same then there has got to be something common between them.


Yes I do.

If this is true, why did you use LBZ pistons in casper's new engine?

Thats what I was getting at earlier, you said the star pattern was to the outside of the piston even with stock tuning, but wouldnt advancing the timing move the star pattern even further to the outside?? Which in turn would not only increase peak cylinder pressure, but it would also place the load further out on the piston....Right? I geuss my point is it seems like it is using the wrist pin as a fulcrum point, so placing the load farther out increases the leveredge it has on the piston. I know you have to advance the timing to make power, but maybe were are going to have to sacrifice a little power for longevity. JMO.

You seem to be forgetting that it is a piston in a cylinder. The piston is guided by the cylinder bore and the loads of compression and power stroke are pretty much equally applied in all directions, (head, valves, bore, piston) including across the surface of the piston. There is no "fulcrum and leverage." There will be localized heating and cooling from the injection flame front and that may affect the suface stress gradient, but not pressure and "leverage."

Tom, you seem to be forgetting that the *pressure* is the same everywhere inside the bore, but the stresses throughout the piston are far from the same everywhere.

If you did a finite element model of the stresses (*not* the load), I think you'd find it was pretty complex. It's not something you can do in your head or on a napkin.

What I believe people are referring to as "leverage" is the model that bending the sides of the piston down over the wrist pin (like two kids on a teeter-totter), at first blush, would appear to impose a tensile stress in the upper skin of the piston (thus creating a crack parallel to the wrist pin). I'm guessing that the tensile force is probably overruled by the general compressive forces from cylinder pressure, but again you'd need a FEA to show it.

Also IMHO, because of the design of the bowl, there is a lifting effect on the upper inner edge of the piston during explosion. I am sure this is also a main contributor to the crack starting.

Tom, you seem to be forgetting that the *pressure* is the same everywhere inside the bore, but the stresses throughout the piston are far from the same everywhere.

If you did a finite element model of the stresses (*not* the load), I think you'd find it was pretty complex. It's not something you can do in your head or on a napkin.

What I believe people are referring to as "leverage" is the model that bending the sides of the piston down over the wrist pin (like two kids on a teeter-totter), at first blush, would appear to impose a tensile stress in the upper skin of the piston (thus creating a crack parallel to the wrist pin). I'm guessing that the tensile force is probably overruled by the general compressive forces from cylinder pressure, but again you'd need a FEA to show it.

You are absolutely correct, but is the stress gradient really substantial point to point (and over a microsecond duration?) or pretty much a neglible difference to the overall stress? Now, I believe the heating/cooling effect across the skin of the piston IS significant, especially with the "quench" effect of injection and vaporization prior to ignition and flame/wave front propigation upon ignition. This would, of course, be severely exascerbated by surface irregularities, carbon buildup "hot spots" and any granular or inclusion subsurface irregularities.

So you've been cutting apart pistons for 3 years and your solution is? LBZ Pistons?

If you had bothered to go back and look at the discussions from before you would find the answer, but I'm sure you just trying to :stirthepo

The bottom line is I feel as does the Diesel Piston Engineer from Mahle the LBZ is the stronger design. Is it all we need NO but it is the best we have right now. What work have you done on trying to solve it?

Play nice. Everyone is entitled to participate here.;)

You are absolutely correct, but is the stress gradient really substantial point to point (and over a microsecond duration?) or pretty much a neglible difference to the overall stress? Now, I believe the heating/cooling effect across the skin of the piston IS significant, especially with the "quench" effect of injection and vaporization prior to ignition and flame/wave front propigation upon ignition. This would, of course, be severely exascerbated by surface irregularities, carbon buildup "hot spots" and any granular or inclusion subsurface irregularities.

Well, I don't know near enough as I need to, but I can think of some of the stress fields that would have to be input to such a model.

1) beam (top of piston) as viewed down the bore of the wrist pin (the fulcrum) with an evenly distributed load applied (cylinder pressure). This creates a tensile force in the upper skin of the piston and a compressive stress somewhere in the piston body. To know roughly where, you'd have to know the moments of inertia on a complex shape. Tricky.

2) heat stress - this expands the skin everywhere, which would act somewhat against the above stress, but would stretch the material at the subsurface. How much stress this generates is a WAG without FEA. The transfer through the soot layer would have to be predicted, the effects of the oil jet in the gallery would have to be predicted, all over what...3ms? Tricky.

3) hoop stress inside the bowl, compressing ths inside of the bowl skin and stretching the OD. Again, for 3 ms or so. Tricky

And that's just a fraction of the whole picture. Without FEA, we're just doing crayon-level engineering here.

...What work have you done on trying to solve it?

Casper's pistons did not crack. ;)

Yup, I'm working on it. But I don't have the time, money, resources, and equip, that the "experts" have, so it will take awhile. I expect to have it working in 2 months if no more problems occur.

...we're just doing crayon-level engineering here.

Just call me The Crayola Kid! :D

Are they any non-destructive tests that could be done to either the LLY or LBZ piston to possibly check for defects? Maybe increase the odds of either of the available cast pistons to live longer?

Pat you said the people using the Ross pistons now wound not use them again, reasons?

Are they any non-destructive tests that could be done to either the LLY or LBZ piston to possibly check for defects? Maybe increase the odds of either of the available cast pistons to live longer?

Pat you said the people using the Ross pistons now wound not use them again, reasons?

X-ray would show any defects in the casting itself.

Casper's pistons did not crack. ;)

Yup, I'm working on it. But I don't have the time, money, resources, and equip, that the "experts" have, so it will take awhile. I expect to have it working in 2 months if no more problems occur.

So in plain English, you have done no work, spent no time, collected no parts trying to figure out why pistons are cracking. When you have please share the pictures and data with those of us that have been working on it and have shared our findings. Until then I think I am safer believing the piston engineering people from Mahle.

As far as non-destructive testing goes it very expensive and there are no guarantees. You would need several X-rays of every piston and you still might miss something

As far as non-destructive testing goes it very expensive and there are no guarantees. You would need several X-rays of every piston and you still might miss something

How much $$$ we talking? I know what the X ray guys clip us for x raying steel pipe and it aint too bad......then again we are talking about a bunch of x rays as well so the $ per probably goes down quite a bit.

So in plain English, you have done no work, spent no time, collected no parts trying to figure out why pistons are cracking. ...

And I'm perhaps further ahead towards a solution than you are from what I can tell. ;)

No more button pushing by either of you.

So in plain English, you have done no work, spent no time, collected no parts trying to figure out why pistons are cracking. When you have please share the pictures and data with those of us that have been working on it and have shared our findings. Until then I think I am safer believing the piston engineering people from Mahle.


And I'm perhaps further ahead towards a solution than you are from what I can tell. ;)
;)

Have any of the coated pistons that have been put in failed? Maybe the coating will take the hot spots better and resist the pitting both of which lead to cracking? Just thinking out loud.

No more button pushing by either of you.




;)

One more round and it would have gotten good.

Casper's pistons did not crack. ;)

Yup, I'm working on it. But I don't have the time, money, resources, and equip, that the "experts" have, so it will take awhile. I expect to have it working in 2 months if no more problems occur.


How much more will it cost when a piston goes south and the entire motor has to come out to be bored and all the pistons replaced, just a few weeks after getting it running?

It's only a matter of time till they break. Out of all the LBZ piston equipped motors running around with over 650 hp, how many are still on the road with a fair amount of heavy use on them? I can only think of 1, Nick's, and I don't recall if there stock pistons, or if they have been modified.

Have any of the coated pistons that have been put in failed? Maybe the coating will take the hot spots better and resist the pitting both of which lead to cracking? Just thinking out loud.

No coated pistons failures yet, but we will know more as they spend more time in service.

Just call me The Crayola Kid! :D Your a riot :funnypost . Do any stand up comedy in between Crayola Hour and DuramaxDiesel 101):h . Keep the humor rollin Pat sombody has got to make it funny once in awhile.

Nick's motor was the first and it has lasted the longest over 14K and still going. No coating, LBZ pistons cut for proper compression and valve clearances. There has also be a failure with coated pistons that I know of as well so that's not the solution.

What was the rest of the configuration on the coated piston that cracked? Was it decompressed? Bowl reshaped? cam, heads, fuelers, injectors, etc? Just because the coated piston cracked doesn't mean poor setup couldn't be the culprit. Perhaps the rest of the setup wasn't very well thought out for each component to work properly with the others. Just thinking out loud.

There is a lot that could be at play here. As we get rid of them one by one we will end up with the cause of the problem and then have a solution. Coating is just trying to cover up what is already at work here. The only issue is that it did not work and everything was setup properly. We got past that long ago. Does it help some......... yes but it doesn't stop the problem so we need to keep looking for the cause if you want something to live. at the High Power levels.

Any pics of Nick's decompressed pistons?

There is a lot that could be at play here. As we get rid of them one by one we will end up with the cause of the problem and then have a solution. Coating is just trying to cover up what is already at work here. The only issue is that it did not work and everything was setup properly. We got past that long ago. Does it help some......... yes but it doesn't stop the problem so we need to keep looking for the cause if you want something to live. at the High Power levels.

The coating should never be viewed as a guarantee to prevent piston failure, only as an aid to raise the threshold at which the piston fails by reducing the amount of heat the piston crown absorbs.

Heat and cylinder pressure are the main culprits. Reducing either one is going to help the piston survive.

I would like to know more about the conditions in which your coated piston failed.

Care to share?

How much $$$ we talking? I know what the X ray guys clip us for x raying steel pipe and it aint too bad......then again we are talking about a bunch of x rays as well so the $ per probably goes down quite a bit.


My old lady is am radioalagy tech at the local hospital I could have her take a couple to work and throw them on the table when no one is lookin!:naughty:

(Takes swig form ice cooled bottle of Labbatt Blue) :)

The following will be my last in-depth post on this subject for awhile. I am not frustrated. I really need to work on my truck. Pulling season is coming fast.

First the following is not meant to be offensive to anyone. If it seems that way it is just my very direct manner.


I thank everyone for sharing their information and ideas on the piston subject. Until today this was very informative and civil.

I will start by saying this. I talked to a Piston engineer also and several engineers I work with about the pistons. I also talked to four of the best and proven “Diesel” Performances shops in the country. Funny they had engineers also. I on my own buck offered to sent each one half of a LBZ and LB7/LLY piston. Two of them said no need as they had already reviewed them. The other two accepted and where sent halves.


Results:


"Stock" to "Stock" the LBZ has the edge. Only because of it wider bowel, larger bowl to piston top radius, and lower comp. ratio. But all agreed that "Stock" was not going to cut it for big horsepower and torque levels. They advised that for my goals that compression should be lowered. The bowl should be widened and the radius should be made larger. The LB7/ LLY piston was the piston agreed to be the best for that. Also they agreed that the LB7/LLY was the better choice if you where to cut in valve relief’s. The reason was the location of the oil gallery. The LBZ oil gallery is better shaped but not as well placed. When the bowl is widened and valve relief’s cut in the LB7/LLY has more material left. This is assuming that the metallurgy is the same and the piston are free from casting defects.


Results will vary depending on what your goals!;)

For me the Ross piston was not a good option. So the two stock choices are all I have.


Like I have said before we need to rethink how we make power. Even if we had a better piston what would fail next? I have said it before. Big power below 3000rpm will break stuff period. The sensible way for me to make big power and have my engine live for a whole season is to rev it up. I did the math and explained the theory earlier in this thread. I first made mention of this a good while back.

11/10/07 I said “As boost goes up compression ratio must go down. A buddies pulling tractor runs 80+psi of boost. His comp ratio is 15-1. These pistons could very well be being split by the forces of cylinder pressure. LBZ has a lower comp ratio but maybe not low enough?”


I still hold firm to that and have never wavered. I truthfully believe there is more going on than just cylinder pressure. Injectors, poor oil cooling, bad casting, and I could go on. But I can limit torque which limits cylinder pressure. I choose to do this because I know this works. Diesel sled pullers do this with great results.

Please be patient and civil about this gentlemen. There some really interesting engine builds going on. Time will tell what works and what does not. If we keeping getting rude about this the info will not get shared. Which would be a great shame.

Hmm Canada has beer figured out that I know for sure.;)

Everyone has to make there own decision when it comes time to build a motor and all engine builders will do it different. What we've been looking for and finding is that these pistons are failing in stock configuration with nothing more than exhaust, air intake and programming. One needs to wonder why it happens to both piston designs. Cracks in the same place, burn through into the oil galley in the same place and they do it with and without big power. Some do it while others do not. Why can 1 motor make Big Power with an LBZ design piston with the top cut, bowl reworked and valve reliefs while another cannot. Why can a LB7/LLY piston do the same, work in one and not another?If it's not a defective piston then what is it? The pistons we are working with are not defective so that means it's something else. The injectors are fine so it rules them out and the piston top shows a good burn pattern. The something else is what needs to be found and repaired or the problems are going to continue for both pistons. We have a pretty good idea what's happening and in what order now and just need to finish with the pistons being sent to us. If the common thread holds true then we've found the root cause and can try corrective action and see if it cures it. This will not happen over night as the testing has to be done to prove it out, but what I can tell you is no amount of coating the piston or decompressing the motor is going to solve it unless you take the power back to stock levels.

We have a pretty good idea what's happening and in what order now and just need to finish with the pistons being sent to us. If the common thread holds true then we've found the root cause and can try corrective action and see if it cures it. This will not happen over night as the testing has to be done to prove it out, but what I can tell you is no amount of coating the piston or decompressing the motor is going to solve it unless you take the power back to stock levels.

Many have offered theories on what is happening. Would it be possible for you to share with us what it is you suspect is happening?

We could speed up the testing by expanding the data set and the entire Duramax community would benefit sooner rather than later. :D

I want to hear about this "failed ceramic-coated piston" engine.

Get the owner to post in here.

I thought the purpose of this site was to help all.

Mods can we merge these threads or have one piston thread? Its hard enough to keep up on one thread.

600+ just started a thread of another possiable failure, LB7 with all the goodies.:(

Mods can we merge these threads or have one piston thread? Its hard enough to keep up on one thread.

Merging them would make the thread a mess, but I have started a new thread for the discusion and made it a stickie.

http://dieselplace.com/forum/showthread.php?p=1725306#post1725306

Guys,

Steve has a good theory at this point but it requires research. There is a lot of information to be learned here and there is no way to speed up the process until a game plan is in place. Lets try to review the theories one at a time and see if we can isolate the benifits for future use. I have not agreed or disagreed with the theory but it does merit further investigation. I also think the coating on the piston will help in many situations but I'm not sure if it will prevent what happened to mine. I talk to all of you guys and you guys are all very inteligent people but we have to work together to defeat the Cummins guys!!!;) :D It's up to Steve if he wants to share the info at this point and there are several other points to be made. In my opinion, it will take a combined effort from everyone to solve all the issues we are seeing. I do think coating the pistons is part of the equation but there are other things to be learned also.

Mcrat is also working on a very useful peice to assist with diagnosing issues like this. At this point, I think everyone should back down the power on the LBZ pistons until we can get a handle on things unless you have unlimited money. Decompressing the piston is also part of the equation.

Let the research and diagnosis begin.

Guys,

Steve has a good theory at this point but it requires research. There is a lot of information to be learned here and there is no way to speed up the process until a game plan is in place. Lets try to review the theories one at a time and see if we can isolate the benifits for future use. I have not agreed or disagreed with the theory but it does merit further investigation. I also think the coating on the piston will help in many situations but I'm not sure if it will prevent what happened to mine. I talk to all of you guys and you guys are all very inteligent people but we have to work together to defeat the Cummins guys!!!;) :D It's up to Steve if he wants to share the info at this point and there are several other points to be made. In my opinion, it will take a combined effort from everyone to solve all the issues we are seeing. I do think coating the pistons is part of the equation but there are other things to be learned also.

Mcrat is also working on a very useful peice to assist with diagnosing issues like this. At this point, I think everyone should back down the power on the LBZ pistons until we can get a handle on things unless you have unlimited money. Decompressing the piston is also part of the equation.

Let the research and diagnosis begin.

Rick,
Are you talking about taking it to a stock power level?

We can't honestly say what power level at this point is going to cause the issue. I'm afraid to post a number because there is not enough data to show a break point in HP. If I owned one I would probably not take it above 100HP over until some further research can be done.

That's just a opinion, there is no data yet to specify a safe HP level.

Rick, Is GM aware of the problem, I realize that these are modified trucks and they don't warranty anything like putting down 600hp , it still seems like part of the problem is with having sufficient quality pistons in our trucks. I would think this will be a longevity problem on stock trucks that are worked hard. Question for some of you smarter guys, than myself, is this just going to be problem on modified trucks. I have heard of another LBZ truck that did not have more than a cat back exhaust and it blew up.

Once the pistons arrive that members are sending in we can get them tested. If after that my theory still holds water we can discuss ways to build a test bed to prove it cures the problem. Remember this problem appears in both piston designs the same way so we will need to test in both application before we know anything for sure.

Even if GM was aware of any issues, the general public wouldn't know it.

The issue needs to be investigated further to determine a viable solution to the cracking. We really need a better piston to with stand the stresses we are putting on them. We are stuck with what's available right now and maybe for another year. I was seriously considering having pistons built but I just can't afford to bite off that expense for the R & D. Mahle has the design specs so I'm assuming it's just a case of the market will not support the investment yet.

We are currently looking at a dry sump option also. Right now there is no magical answer to all the issues so we are building what we think is the best solution at this time. Tomorrow that could change but right now we are still on the same path. We should be up and running next week with a complete new set up so we'll see how it works.

We boxed up the pistons and we will be sending them to Steve (TTS) for further evaluation. I believe Mahle will be involved also. Trippin also has a piston for review.

Warning......do not copy my 2 piece variable compression piston technology, I'm currently trying to market it to the Cummins guys!!!!:eek:

Warning......do not copy my 2 piece variable compression piston technology, I'm currently trying to market it to the Cummins guys!!!!:eek: :thumb: :D

We boxed up the pistons and we will be sending them to Steve (TTS) for further evaluation. I believe Mahle will be involved also. Trippin also has a piston for review.

Warning......do not copy my 2 piece variable compression piston technology, I'm currently trying to market it to the Cummins guys!!!!:eek:

Taz I am trying to remember, but with everything that has gone on lately....

Anyways.

Were you the one that was pushing the LBZ and had an issue (thought to be a rod or piston), and found out you had a chunked ring? If so, what were you pushing the motor too approx HP/TQ? If I am remembering correctly you reassembled it and ran it some more until the piston failed (am I right)? If so, what changed (turbo, injectors, tuning, etc) after that to make the piston fail?

Originally we thought we had a head gasket issue or something but it ended up being a broken oil ring. While we were in the motor we found the rods had bent. We changed the rods and went back together then the piston broke. I can't remember the exact chain of events but I have always ran the same set up with no issues for about 7000 miles. The HP were about 715HP-750HP