We're dealing with my 2001 LB7. I had a set of Crower Rods from Socaldiesel (Trippin) put in while I was waiting on my heads. New bearings and piston rings, stock LB7 pistons went back in. The heads showed up today but they ran into a BIG problem.
Normal piston PROTRUSION above the block on full stroke is supposed to be between .008 to .012". I think I was in the .010 range stock b/c they ordered the "B" gaskets for the rebuild.
Today, going back together they measured my PROTRUSION to be .019-.022!! :eek: :eek:
They want to know what I want to do....I have no idea! I guess they called Guy (Trippin) and he said the only thing he knew was to mill the pistons. Isnt that going to make my already weak LB7 piston even weaker? Has anyone else just plain milled pistons before? Wont that cause the dreaded sharp edges in the bowl?
WHAT SHOULD I DO?!? This really sucks!
P.S. The only thing I can think of that caused this is that the Crower rods are not the same length as my stockers....It shouldnt be this way, should it?

The other option that the dealer gave me was to put a head gasket on for an LB7 that has been overbored .030. I guess they are thicker, but this moves my fire-ring out that much further and they dont think that it will work.

I'm open to any and all ideas! :help2:

Sounds like a rod problem, did they measure every piston?

It sounds like they might not be getting an accurate protrusion measurement. If the rods were too long, I would guess others with rods from the same run would be having that problem too.

If it does end up that you have over achieving rods, then don't worry about weakening the pistons, your only option is to machine them, you shouldn't have a problem.

I would have them check rod length to start with. If they are wrong then what else might be wrong. Start by checking one rod if it's to long then pull them all and get them inspected. The over bore engine gasket shown in the service manual has not been able to be purchased so far but maybe your supplier can find them somewhere besides GM. If you decide to mill the pistons make sure and check your compression ratio. The stock ratio is 17.5 as long as the protrusion is in the proper range. By milling the pistons just to get back to stock you have also reduced the volume of the chamber in the piston some amount so that would raise compression and I do not believe that is what your looking for.

If you decide to mill the pistons make sure and check your compression ratio. The stock ratio is 17.5 as long as the protrusion is in the proper range. By milling the pistons just to get back to stock you have also reduced the volume of the chamber in the piston some amount so that would raise compression and I do not believe that is what your looking for.
Definately not!
Thanks for the pointers guys! I guess I'll have them start by pulling one piston and measure that rod and compare it to my stockers. I may have them put a stock rod back on that piston and check the protrusion again.
Maybe something different with the new bearings?
This is turning out to be a hell of a lot more than I thought it was going to be!

Did you have the block prepped? Did they deck it?

They prepped the block(cleaned everything up), no decking was done. Cripes, they were worried about Guy cleaning up my heads when/where the fire-ring chewed them a little.

did they line bore the mains?

I spoke with the engine builder yesterday and suggested they install a stock rod and check the piston portrusion in order to verify a rod length problem.

Assuming the rods are too long we could exchange them, however we all know how hard it is to get rods these days. :(

A refund is always an option...............

Anybody want to buy a set of Crower's that are potentially .010-.012 too long? :D

Lastly, we could mill the top of the piston for the proper portrusion and then re-radius the bowl and/or recontour the bowl to get the compression back to stock or less. At 17.5:1 it doesn't take much to move the compression around.

I'm having a hard time getting them to put a stock rod back on. They've got the bottom end all back together and flywheel on and dont really want to re-do it. I'm thinking they are going to have to. The bad part is, they are a John Deere dealership/GMC dealership and they are getting into their busiest 6 weeks of the year.
I thought they had measured the protrusion before to get the gasket size, but the builder told me that they just went off of the old gaskets. The pistons and block were carboned up and they didnt measure it then--No baseline.

The builder thinks the overbore gasket will get me in spec(due to the fact it is for .01-.03 overbore and .008 block deck), but I'm not overbored. He is checking on availability after I told him what Steve said.

My tallest piston protrusion is .022

I guess what the builder wants to know is:
How much will the rods stretch/grow when they heat up? Compared to stock also if anyone knows.

If the rods were somehow too long, wouldnt there be a whole batch that would be too long, not just one particular set?

Tomac: As far as I know all they did was put new bearings in, nothing else.

Guy, I dont plan on sending the rods back! If anything I'll get my pistons taken care of first.
If the rods are a little longer, does that now make me a stroked motor? :D

Hey Max, sorry to hear about all your problems. Hope someone gets it figured out back there. This is probly the biggest build they've done to a duramax so I'm sure they are learning as they go. Which mechanic do ya got working it?

It may be that the measurment that they took is wrong due to where they measured from,The measurement needs to be taken at the center of the bore or over the wrist pin otherwise your #'s can be way off.I would make sure of how they checked them,ask how and where they did it before asking them to remeasure if it wasn't done thios way.

good luck

I'll have to ask them where they took it, I dont know. They pretty much do everything right off the GM manual, so if thats how the manual says to measure it, thats how theyre doing it.
I know they cant measure rod length from center to center with the tools they have though.

Hey Max, sorry to hear about all your problems. Hope someone gets it figured out back there. This is probly the biggest build they've done to a duramax so I'm sure they are learning as they go. Which mechanic do ya got working it?

Randy Dvorak is the one I've been dealing with the most. I think its a guy named Jim that is doing the actual labor on it though.

Max

Have them check to see if they can really get the overbore gasket before you make a decision as I have not found anyone that has been able to get them in the past. If they cannot get them the only choice would be to cut the pistons if your keeping the rods as is.

A gasket for overbore has nothing to do with this. The pistons are still stock bore, why an overbore gasket? Its not going to be an thicker. If it wont fly with Grade C's at .042" thick, your gonna have to find another way to fix it.

Decking the pistons is a great option, but not until you know how ALL of them fit in each bore. This is something that will take a bit of time to measure up properly.

On the tallest piston with the .042 "C" gaskets I would still be .005 taller than spec. Is that enough to worry about?
If it is enough to worry about, the only way I see doing it RIGHT is to do like Eric just said.
Thanks for all the input guys! Ill keep you posted and let me know if you think of anything else!

Ok guys, I got to make a decision today. Is the .005 over spec on one cyl. enough to get me into trouble or should I just put the "C" gaskets on and forget about it?

Eric, Steve, Do you guys check protrusion on most/every motor that you put rods in? Do you see much difference from stock?

Are the Lb7's Mahle pistons? On the 7.3L's Mahle has a reduced compression piston that is there for engines that need to have the blocks decked. They move everything down 0.010". Do they have this for LB7's???

You measure and correct every piston in every motor. The people we work with keep the piston protrusion + - .0005" for a total variation of .001". Yes, you need to worry why your seeing a problem and correct it.

Eric

The reason for the overbore gasket is the fire ring is moved making a larger area to help lower compression and there are two gaskets for over bore and one is thicker than the "C" gasket that's why they would help. Only problem is we have not been able to get either of them in the past so it looks good on paper but so far cannot get them but were still working on getting them.

Its getting sent off to an actual machine shop. I was going to send it Eric's way, but the dealership knows a place that got "machine shop of the year" in Vegas just an hour away and they had someone heading that way already. This way it can be done as Steve had said, every piston done the right way, and it will be balanced.

How far down are most going with their compression? I'm not too fond of going much below 16:1, I want it to start OK. Its only gettin a GT 4094 put on it for now.

I have built and repaired International, Isuzu, Cummins, Detroit and CAT. I have never rebuilt or repaired a Duramax. However, in also building performance gas I would say that the rods are screwed. Someone screwed the pooch. Again, not being a Dmax builder, all of the diesel I have worked on has forged rods. I can't believe that stock Dmax rods are weak. My point being, why can't you use stock replacement rods?

In as far as removing one piston and checking rod length, it should not matter if the flywheel is installed. The pan has to be removed to access the rods. One rod and piston assembly can be removed without that big of a deal unless they did an inframe repair; or did they R&R the engine assembly. If they have the engine on the stand then the thing has to just be rotated over and the pan removed to get to the rod.

If you gave them the parts, and if they are screwed up and do not fit, you are responsible for the extra time it will take to check this out. If they supplied the rods and its screwed up, then they are responsible for the problem and have to eat the extra time to get it right. That is usually the way shops see it. However, if you can get them to admit they screwed up and did not properly check the parts out before assembly then maybe they will recheck it without further cost to you. Don't hold your breath.

You asked if you would have a stroker setup. This involves also having a modified crank and pistons to match up with the longer rod length of such a setup.

Bottom line is: if the pistons are stock; if the crank is stock; if the block is stock; if the block has not been decked; the rods are at fault. Get stock rods or make the rod supplier come up with the correct fit. If you machine or cut something and it fails then you eat the price of what you modified too.

I have always had a business motto that has done me well: NO BAD DEALS. This whole scenario is a bad deal in the making looking for a place to happen. I hope for a good outcome for you.

My $0.02 from an old fart.

Good point on the rods being out of spec. What do folk do when we just want to replace our stock rods and reassemble the engine and reuse all the stock heads and such ?????????????

Good point on the rods being out of spec. What do folk do when we just want to replace our stock rods and reassemble the engine and reuse all the stock heads and such ?????????????

Thats exactly what I was looking to do to begin with. I had a head gasket failure and had to have some head work done b/c the fire-ring on my head gaskets grooved the heads. I thought wile the motor was out (easier to work on and do head studs) I just as well do the rods so I wouldnt ever have to pull the motor again (hopefully).
So, I guess the question is: Eric, Steve, or anyone else who has done a few of these, have you had to do piston work on all the motors that crower rods have been put into them? Am I the first trying to "drop in" aftermarket rods with my remaining stock internals(ie, has everyone else who put crowers in opted to do piston work to begin with)?
I will send some stock rods along with the rest of my motor and have the machine shop take some measurements. If the rods are off on measurement, I may have to take you up on your offer Guy. I'm sure I can find some rods somewhere.
Keep the inputs coming guys, I really do appreciate it!

I can't believe that stock Dmax rods are weak. My point being, why can't you use stock replacement rods?
There have been more than a few threads on here lately about people who are adding extra boost and fuel are finding the next weak link is the stock rods.
In as far as removing one piston and checking rod length, it should not matter if the flywheel is installed. The pan has to be removed to access the rods. One rod and piston assembly can be removed without that big of a deal unless they did an inframe repair; or did they R&R the engine assembly. If they have the engine on the stand then the thing has to just be rotated over and the pan removed to get to the rod.
It is out and on a stand. There is a skirt inside the pan that they didnt want to take off too bad, they also think I'll need another set of new main bearings.
If you gave them the parts, and if they are screwed up and do not fit, you are responsible for the extra time it will take to check this out. If they supplied the rods and its screwed up, then they are responsible for the problem and have to eat the extra time to get it right. That is usually the way shops see it. However, if you can get them to admit they screwed up and did not properly check the parts out before assembly then maybe they will recheck it without further cost to you. Don't hold your breath.
Its at a GMC dealership. I gave them the parts, I expect to pay for the labor they are putting into it. They are not into the aftermarket performance stuff, its a learning experience for all of us. I'm sure if either one of us had the choice, it would have been taken somewhere else. I initally hoped my head gasket failure was injector related, thats why it went to GMC.
Bottom line is: if the pistons are stock; if the crank is stock; if the block is stock; if the block has not been decked; the rods are at fault. Get stock rods or make the rod supplier come up with the correct fit. If you machine or cut something and it fails then you eat the price of what you modified too.
The only thing not stock was the rods. Engine was not decked, pistons were left stock. Crank/rod bearings were replaced, main bearings were replaced. I'm wondering if maybe they go a little carried away cleaning up the carbon they said was in the way from taking initial measurements? I dont know how they cleaned it for sure, but I know they didnt deck the block.
I have always had a business motto that has done me well: NO BAD DEALS. This whole scenario is a bad deal in the making looking for a place to happen. I hope for a good outcome for you.
I too saw the bad deal in the making, thats why the motor is now sent off to another shop to GET DONE RIGHT.


Great insight/post. Thank you.

The rods may be off a tiny bit, but i wouldnt sweat knockin 0.010"-0.012" of the tops of the pistons. that wouldnt weaken them enough to worry about.

We have always taken some off some of the pistons as the stock motors do not hold the numbers we do when assembling a motor. The issue comes from, if the length is wrong what else? They could be perfect everywhere else but it's best to slow down now and check so you will not have to later. I have no issue with removing .020" off the top of the whole piston. Since your going to this effort to get it right I would see about getting the final compression ratio down to the LBZ level which is 16.8 Vs the LB7 17.5 if you can without removing to much metal.

After reading and posting last night I have been looking at different diesel performance sites. The most interseting one was Banks Engineering. I don't know if Banks developed their own rods, but they did install performance rods in the diesel truck they have developed. It is the Cummins/Dodge and it has a single turbo. It is 700 plus hp and over 1000lbft of torque. They also showed some build being done on the Dmax they used for nearly the same stuff. They used the stock block; they used the stock crank but machined for knife edges; they used stock heads but tricked them out; they used non-stock, performance, forged, light-weight pistons and rods.

Since Banks is so friendly and has really great tech support, I would suggest getting in touch with them and see if someone on their R&D staff would have some recommendations or tips they are willing to share.

Let us know what happens with your engine. I am sure many want to find out what you did to overcome this toughy.

Regards

After reading and posting last night I have been looking at different diesel performance sites. The most interseting one was Banks Engineering. I don't know if Banks developed their own rods, but they did install performance rods in the diesel truck they have developed. It is the Cummins/Dodge and it has a single turbo. It is 700 plus hp and over 1000lbft of torque. They also showed some build being done on the Dmax they used for nearly the same stuff. They used the stock block; they used the stock crank but machined for knife edges; they used stock heads but tricked them out; they used non-stock, performance, forged, light-weight pistons and rods.

Since Banks is so friendly and has really great tech support, I would suggest getting in touch with them and see if someone on their R&D staff would have some recommendations or tips they are willing to share.

Let us know what happens with your engine. I am sure many want to find out what you did to overcome this toughy.

Regards

Banks developed Dmax rods in conjunction with Crower a couple of years ago. They have since switched to the Carillo pieces. Wouldn't exactly call the crank knife edged, but the did round the leading edges. A lot of the hotrodding we are doing today was developed by Banks starting in 2004, IIRC.

I would be VERY surprised if Crower missed the eye to eye by that much on a set of rods. Rod mfr's are used to measuring things down to .000050", or half a tenth.

Something is odd. 0.015" is the thickness of a matchbook cover. If it's not too late, look at it. Depth mics are easy to misread. Whenever you get a bad reading on something, if you can, use a secondary method for measuring, like in this case, it would be a surface gauge with a dial indicator clamped on it.

What's up? Does it run? How did it all go?

The motor and heads are all sitting at the machine shop waiting for them to look at. They do a lot of work for Saleen and do Cobra's, and just got 3 motors in before I got mine in plus they had 2 cars in the lot to get to also before they even look at mine.
They have no problem decking the pistons, but are not too comfortable doing anything to the bowls to help in lowering compression.
They're going to measure my stock rods and the crowers to see if there's something up there.
I may know more next week, but as of now I'm at a standstill.... :(

jason hope everything is going well and they have got everything figured out, keep the salad boys updated on the build

Hey Max, how's the engine build coming? I was up to St Paul Equip. the other day and didn't see your truck in there. Hope it's coming along for ya!

My wife picked the motor up in Hastings for me on Friday and dropped it off at St Paul. Everything should be there now for it to go back together--I HOPE! I think they are going to get to it the first thing next week. I had her take some pictures of the pistons since I didnt figure I'll ever get to see them otherwise. They are still on the camara but when I unload it I'll try and post some pics.

Man that sucks, I hope you get it all worked out. I hope I don't run into a similar situation with mine. Good luck.