I'm not sure where this should go so the moderator should move it if I screwed up but I wanted everyone to see this.

I was told I needed to post this so everyone would have the info.

All 8 of my LBZ rods were bent. The LBZ rods WILL bend at approx 600-650RWHP. A few of them were bent pretty good and they will not hold the power everyone (including myself) thought. I'm only posting this to provide people with insight to the strength of the LBZ rods so they don't explode motors. I have just given away a advantage over others but it's the right thing to do.

The rods are bent in the same place they always bend and the worst one is about .030" which makes no difference, a bent rod is a bent rod.

I think this provides people the information they need to make a informative decision.

GM just can't get it right, i saw them with my own eyes. You can make over 1600HP on stock cummins rods(10 times stock). Is it too much to ask for GM to give us rods to hold a measly 3 times stock power?

Maybe the dyno was wrong and I actually was making 1812HP the dyno just forgot to put the 1 in front of it!!!:D

Are the LBZ still fractured rods? I believe the process of how they are made and the material is the problem, when they start with powder steel... It will hold stock power and it is quick and cheap, which gets the motors out the door and keeps the cost down.. But when comes to hold power they just will not cut it.
Jon

Its good to know that they are still a weak link. Im really surprized that they will handle what they do.

Dual pumps, big turbo you are going to blow it up. Build it first...

Dual pumps, big turbo you are going to blow it up. Build it first...

Hasn't Tomac been running the stock rods on his first/stock motor? That motor made it awhile under a lot of abuse. How much are we talking in "building it first?"

http://dieselplace.com/forum/showthread.php?t=135057

its a V8 vs. an I6. The I6 is always going to be stronger regardless so stop blaming GM.

I don't think the connecting rod knows that it is in a V-8. All it knows is that it is trying to transfer X lbs of force to the crank.:)

Hasn't Tomac been running the stock rods on his first/stock motor? That motor made it awhile under a lot of abuse. How much are we talking in "building it first?"

Quite a few guys put their engines through a lot of abuse. When twin pumps became available, the HP jumped way up as well as all the things that go along with high HP(CP,etc.)

Micheal will have to comment if it lasted with twin pumps.

I'm not sure where this should go so the moderator should move it if I screwed up but I wanted everyone to see this.

I was told I needed to post this so everyone would have the info.

All 8 of my LBZ rods were bent. The LBZ rods WILL bend at approx 600-650RWHP. A few of them were bent pretty good and they will not hold the power everyone (including myself) thought. I'm only posting this to provide people with insight to the strength of the LBZ rods so they don't explode motors. I have just given away a advantage over others but it's the right thing to do.

The rods are bent in the same place they always bend and the worst one is about .030" which makes no difference, a bent rod is a bent rod.

I think this provides people the information they need to make a informative decision.

In this post (http://www.dieselplace.com/forum/showpost.php?p=1590039&postcount=19) you said "The rods are not bent, the piston protrusion is with in .002 accross the deck so I'm cofident there is no rod issue."

Are you talking about the same rods?

2 different times checking. The rods were bent then, I just didn't tell anyone until I got them out to prove to myself they were bent.

Yes, I with held information until now so I guess I need my flame suit on now!!;) Geeez.....I can't give out all the secret information!!;)

I'm glad that you decided to post the real results.

I'm not sure what your motivation was for not posting it up front, but it was your choice.

Could have been a bad deal for someone if they swapped to a LBZ bottom end before seeing this...

The reason I didn't post it was because I had not measured them and there was no-one applying the power yet. It had nothing to do with not wanting to post the information but sometimes I'm cautious about what I post. I'm not going to get into details but the bottom line is the LBZ rods are stronger but as proven, they aren't strong enough.

I felt there were a lot of people relying on the LBZ rods and I saw the need to correct a potentionaly bad situation for others and maybe save a few motors.

its a V8 vs. an I6. The I6 is always going to be stronger regardless


are you flipin serious!!!!?!?!?!???

are you flipin serious!!!!?!?!?!???


well fine, you're the genious, explain to me, what should GM have realistically done to make the engine as strong as a cummins.


so basically you're saying its unacceptable that these engines are breaking when we ask them to produce 3 times what the factory designed them for? are you flipin serious???!!?!?!!?

They are designed to run 3xx hp and plus a built in safety margin above that. I don't think it is realistic to think that GM should have built the rods to hold 600+++ hp. They definitely could have done that if they wanted to but it is way overkill for their application.

If you keep them stock I am sure you could run the to 500,000 miles + and never see a bent rod.

well fine, you're the genious, explain to me, what should GM have realistically done to make the engine as strong as a cummins.


so basically you're saying its unacceptable that these engines are breaking when we ask them to produce 3 times what the factory designed them for? are you flipin serious???!!?!?!!?

maybe you missed the sarcasm in my post there, partner.

Try to chill a bit and think before you take things so literally and become mr defensive for GM. I love GM, I wouldn't have anything else, NO I DON'T think it is unacceptable that they break with 3 times factory power, what point would there be in making them strong as a cummins for the .0000066 % of duramax owners that are going for 3 times stock power.

If you were really asking(i'm not sure). It is obvious what is needed to make them stronger. Rods, etc.

wooosaaa wooooosaaaa
http://i.imdb.com/Photos/Ss/0305224/th-C116-19A.jpg

Try to chill a bit and think before you take things so literally and become mr defensive for GM.

http://www.dieselplace.com/forum/showpost.php?p=1625401&postcount=25

Sorry, I just didnt detect any sarcasm in your first post, no hard feelings.

well 99.9% of the time there will be some


Rumor is that the LMM's have crowers, thats why they have been soooo behind in being able to sell to the public

GM just can't get it right, i saw them with my own eyes. You can make over 1600HP on stock cummins rods(10 times stock). Is it too much to ask for GM to give us rods to hold a measly 3 times stock power?

I think someone should start a class action suit :rolleyes:

2 different times checking. The rods were bent then, I just didn't tell anyone until I got them out to prove to myself they were bent.

Yes, I with held information until now so I guess I need my flame suit on now!!;) Geeez.....I can't give out all the secret information!!;)

Actually had you witheld information, you'd have sidestepped any questions about the rods rather than stating that they were OK. There's less danger in the former...

Love all the Secret Squirrels attacking Tazman for not posting enough data.

What are some noticable symptoms of bent rods? For an LB7, LLY, LBZ or otherwise.

"The rods are not bent, the piston protrusion is with in .002 accross the deck so I'm cofident there is no rod issue. The parts are arriving dailey to build a stronger peice and I hope this give's people some insight on what it costs to do this. In my opinion, if you are running a high HP tune up, you are on borrowed time. I will post some pictures at the end of the week, there are a few guys that have the pictures already so we have a pretty good understanding what happened. Luckily my wife has a good understanding of what it takes to run this hard so she has given me some latitude to build this thing right but if I break it again, I'm sure her understanding will diminish at a high rate of speed!!http://www.dieselplace.com/forum/images/smilies/eek.gif"


This was my original post and the pistons were within .002 of each other but I didn't check the actual protrution until after the pulled the piston and saw the distortion in the rod. The rods are with in .002 of each other in length but they were all bent. I never dreamed they would all be bent the same. I guess I should have just kept the info to myself?:mad:

Love all the Secret Squirrels attacking Tazman for not posting enough data.

Are you reading a different thread than me?

Be nice to know yours and everyones cylinder pressure is when you made your max power before or at when the rod/rods bent. Then again this is woulda coulda to late and only a few can do this. Anyways thanks for posting your facts for everyone to read as it puts everything in perspective.

Since this go fast Max stuff is new to me I gotta ask the question & deals with the flaming answers, If your making a bunch of power in itself won't bend the rods but I'm guessing big cylinder pressure. If I assume correctly then would giving up a couple degrees timing would not still make big power but reduce a little cylinder pressure & make it live alittle longer?

It's a balance to find the maximum power at the lowest cylinder pressure. Contolling burn rates is what causes the cylinder pressure spikes. If you can get the fule in and control the explosion during the compression stroke then you can make the engine live. When the rods bent, there was not a lot of timing in the tune up but there are so many other variables that we were looking for spikes initially.

Judging from the pistons, I think we were pretty safe on the heat but the pressure was just a little more than the rods could take. At least we were making the power equally accross the cylinders since the rods all bent the same.

I don't want to beat a dead horse or ride Ric here, but I have to ask:

If the piston protrusion was within .002" but the rods were bent .030" what was the original protrusion?

Or did I read something wrong here?

That is exactly why I think tunes for high horsepower(dual pumps and big turbos) that are designed with cylinder pressures being monitored would be well worth it. I am not saying that I would keep stock rods for that type of power, but even with aftermarket rods it would be nice to have a tune that was less stressful on an expensive motor.

You would have noticed .030 bend in the rod by not seeing the piston come up flush or proud of the deck. I wasnt there to say either way, but I've seen enough bent rods, its usually pretty obvious.

Regardless, Ric proves the LBZ rod is not what it was thought to be.

Yeah since all was bent would be a good indication everything was as equal as you could be and that the pressure was to much for the rods to handle. Maybe this dosen't apply...when I dynoed my gixxer1000 I spent some hours tunning it until I got the maximum power I could. The engine would heat up fast on the dyno even with three high velocity fans blowing on it with the plastic off from the load of the brake on the dyno. Never would the thing get hot during a 1/4 mile pass even with the plastic on in a 98 degree day, Do you think when you guys are loading these trucks on the dyno that your doing the damage or starting the damage to the rods from the stress the engine is seeing on the dyno compared to just running it on the street/strip? Or maybe I should ask do you see the same boost/egt's and load(if you could measure) on the street and strip as you do on the dyno?? Just wondering if a guys that wants his engine to live should not spend alot of dynoing time from the abuse the dyno could cause. I guess it depends on the dyno how its loaded would make a difference too. Sorry for rambeling.

I'm tired of defending this post for information I passed along to save people money and provide people information. I'm not obligated to provide any explanation or info but I feel I have been more that helpful with providing what is needed to build this kinda power and what the results could be.

I'm tired of defending this post for information I passed along to save people money and provide people information. I'm not obligated to provide any explanation or info but I feel I have been more that helpful with providing what is needed to build this kinda power and what the results could be.

Sorry guys, but Ric is a little stressed here lately for obvious reasons. I would like to answer a few of your questions on Ric's behalf if I may. As to the question about the dyno putting to much stress on the truck compared to the street or track I am going to have to say no because I can't put enough load on the truck to get the same boost level as he sees when pulling. The biggest problem with the LBZ IMHO is the computer system is way too smart and monitors way too much **** for it's own good our the motor for that matter. "Torque Management" is hell on the motor at these power levels and that is what actually bent the rods in our case. It is the same reason why Ric doesn't want to show you guys the dyno numbers because we are fighting the TCM and PCM trying not to cause the TM fuel cut issue. When it does it's "Torque Reduction" it pulls the fuel for a spit second and then when the sensor readings make it happy agian it sprays the fuel agian. Guess what, turbo didn't slow down and was still pumping the air in, and when it resprays the fuel it creates one hell of a turbo bark/compressor surge and cause the truck to damn near jump off the dyno it is so violent. You guys can take the info for what it is but we are just trying to help everyone out here so if you don't want to know about it or want to keep poking at us we will quit sharing the info. As far as we all knew the rods were fine until we pulled them out and laid them next to the new ones and saw the problem, I would have posted the same thing, oh well we ALL make mistakes. I will show you what it looks like on paper and maybe it will make more since to you. This truck makes big power and is even stronger now with the new build and will only get better as time goes on and fix the computer issues. I am looking forward to a great pulling season with Ric and Larry's trucks as I have invested a TON of my personal time into both and would not have it any other way. I truely love what I do and enjoy the building process and it is alittle scary to be the first out on the limb so to speak with the LBZ but in the end it will all be worth it.

http://www.dieselplace.com/forum/attachment.php?attachmentid=34917&stc=1&d=1172803856:idea:

Sorry guys, but Ric is a little stressed here lately for obvious reasons. I would like to answer a few of your questions on Ric's behalf if I may. As to the question about the dyno putting to much stress on the truck compared to the street or track I am going to have to say no because I can't put enough load on the truck to get the same boost level as he sees when pulling. The biggest problem with the LBZ IMHO is the computer system is way too smart and monitors way too much **** for it's own good our the motor for that matter. "Torque Management" is hell on the motor at these power levels and that is what actually bent the rods in our case. It is the same reason why Ric doesn't want to show you guys the dyno numbers because we are fighting the TCM and PCM trying not to cause the TM fuel cut issue. When it does it's "Torque Reduction" it pulls the fuel for a spit second and then when the sensor readings make it happy agian it sprays the fuel agian. Guess what, turbo didn't slow down and was still pumping the air in, and when it resprays the fuel it creates one hell of a turbo bark/compressor surge and cause the truck to damn near jump off the dyno it is so violent. You guys can take the info for what it is but we are just trying to help everyone out here so if you don't want to know about it or want to keep poking at us we will quit sharing the info. As far as we all knew the rods were fine until we pulled them out and laid them next to the new ones and saw the problem, I would have posted the same thing, oh well we ALL make mistakes. I will show you what it looks like on paper and maybe it will make more since to you. This truck makes big power and is even stronger now with the new build and will only get better as time goes on and fix the computer issues. I am looking forward to a great pulling season with Ric and Larry's trucks as I have invested a TON of my personal time into both and would not have it any other way. I truely love what I do and enjoy the building process and it is alittle scary to be the first out on the limb so to speak with the LBZ but in the end it will all be worth it.
Thank you for answering my question. I asked for future dynoing. I like to ask questions and sometimes might ask to many but I take everything in and learn from it. All of you that have posted this valuable info for us average guys to read and learn from help us from making mistakes or wondering if I will get away with this or that. Could you imagine the carnage from blown motors if you and others on here(you know who you are)didn't post anything about what works, how it works, it's limits and why and how it blew up?? You'd have guys buying this product and that product and putting together time bombs and not knowing it. Thanks again!

I think what Ric is saying on the protrusion is that each cylinder was within .002 of all the other cylinders, not actual protrusion of the deck.

GM just can't get it right, i saw them with my own eyes. You can make over 1600HP on stock cummins rods(10 times stock). Is it too much to ask for GM to give us rods to hold a measly 3 times stock power?


well they are stock cummins rods but the have been strengthened and duramax are not. but like every one said u know all. keep it up

Taz,

Thanks for pushing the LBZ to these power levels and keeping the community updated on your sucesses as well as your setbacks. I personally feel you have saved many people lots of money by sharing your information.

:ro)

You just probobly saved my motor. Imagine this site didn't exist this guy (tazman) has no obligation to share anything. That weird that they ALL bent.........CRAZY. Guess I'll be getting rods before the turbo..:(

I'm glad I didn't get LBZ rods. Thanks for the info.

hell yeah man thanks for the info!!:ro)

Taz,

Thanks for pushing the LBZ to these power levels and keeping the community updated on your sucesses as well as your setbacks. I personally feel you have saved many people lots of money by sharing your information.

:ro)

I'm not engine builder, so take my oppinion with a grain of salt, but I agree with this position.

Nobody is in any way obligated to "give" out information unless they're trying to sell something or make a profit from it, and one person's oppinion or experience should not be enough to completely change a good builder's oppinion.

don't ever think your truck is oblivious to engine failure. i didn't take the warnings and look where i am now. no i don't have and lbz or lbz rods, but that doesn't matter. i have a blown engine due to having a closed mind. build, build, build. it's worth it in the long run.

taz:

did you window this block, or how did you know you had bent rods, smoke issue, compression test lower than normal? what is normal copression on the lbzs

any pictures to help me along with what was bent on the rods, will the older crower rod on the lb7 work on the lbz? or is their maching to be done to it as well

we just installed a gt42 on a buddys lbz with a dual fueler, if i would of seen this thread a few weeks sooner i maybe would of held off and done the rods as well, i guess i am looking for rods now....

thanks for the info

taz:

did you window this block, or how did you know you had bent rods, smoke issue, compression test lower than normal? what is normal copression on the lbzs

any pictures to help me along with what was bent on the rods, will the older crower rod on the lb7 work on the lbz? or is their maching to be done to it as well

we just installed a gt42 on a buddys lbz with a dual fueler, if i would of seen this thread a few weeks sooner i maybe would of held off and done the rods as well, i guess i am looking for rods now....

thanks for the info

Thats basically what I was asking before, and have yet to get an answer. How did you know they were bent, or think, before you removed them? Did you put a window in her? Smoke issue? Odd compression? Noise? Like someone said previously, I don't know much but read all that I can and take in everything I read and learn from it. What I know now, compared to what I knew 3 yrs ago when I bought my truck is an enormous amount, although there is still TONS to learn. All of the great folks on this site deserve the credit as my teachers. There is a lot of BS on this site, but once you figure out who knows what, the information available is priceless. Thank you Dieselplace and all of you that really know your stuff, you dont' need to be told who you are.

If I missed it I apologize, but is it 650 crank or 650 rear wheel hp that bent the rods. Thanks.

I knew something wasn't right when we stopped progressing on the dyno. We were at almost 740RWHP with the stock rods but after approx 620RWHP we started having to make major changes to get any response and I think we were hurting the rods then. I thought it was tuning related but I spoke to some of the best tuners in the country and we all agreed there was another issue. The balance rates still showed ok except for #8 and the truck showed no signs of damage and it ran great on the street. I had a gut feeling that something was not right.

After talking with a few guys Mark and I made a spur of the moment decision to pull the heads and see if anything was happening. We found the issue with #5 piston but all the other cylinders looked great. We stuck a dial indicator on the deck and zeroed it then just checked TDC of each piston and they were within .002 of each other but I didn't check actual protrution above the deck. Since they were all equal, I stopped there and sent the heads to Trippin and waited until the heads returned to pull the piston and see what actually happened. Now I must give credit to Steve (TTS) because this is what he actually said to me..."are you out of your mind, you need to check the rod length when you get the engine apart and make sure they are not bent"....which Kyle (CrankItUpDiesel) did for me when he was there and found they were all bent. Before I knew for sure if they were bent, Steve had already sent me rods and they were on my door step the next day so he was looking out for me. You have to remember that we completly rebuilt the engine and trans over a 30 hour all night build that resulted in one stout LBZ. Make no mistake though, everything was checked and rechecked by a second person in order to avoid any mistakes when building this truck.

Here is what everyone needs to get out of this, the engine really didn't show any signs the average diesel guy would have picked up on and if we weren't on the dyno, I'm not sure we would have picked up on it. The truck would have lasted awhile with the bent rods because of the lower compression but it's not right. Despite the fact the trucks are lasting a while at this level is not a indicator of what is truely happening with the engine and what WILL eventually happen if the engine is left at the high HP. I'm sorry if people feel I should have posted the issue sooner but I wanted to make sure everything was correct before I passed on the information. I would be willing to bet there are a lot of motors out there that have bent rods and the owner doesn't know it at this point but hopefully everyone will now be a little more cautious on the power.

This is my opinion for what's it worth, I would put rods in the motor before I did any major power adders just to have the confidence that the rods will hold up. That's just my opinion for what it's worth.

Thanks Ric. I'm glad you were able to find the limits of these rods before any catastrophic failures.

Anybody that pushes the limits of these is bound to get flamed somewhat. Remember the Nasty Girl threads?

Hats off to those involved!

When your heads are off you can measure piston protrusion above deck height. With a straight rod the piston should protrude .008 to .014 above.

http://www.dieselplace.com/forum/attachment.php?attachmentid=34942&stc=1&d=1172846802
# Use J 7872 to measure the piston projection across two different points on each piston.
5.1. Zero the dial indicator to the cylinder deck surface.
5.2. Place the dial indicator pointer on the piston top. Be sure the pointer is directly above the piston pin centerline to prevent inaccurate readings from piston rocking.
5.3. Rotate the engine to roll the piston through Top Dead Center while noting the maximum reading on the dial indicator.]

You can measure this with a dial indicator or if you don't have one you can use a straight edge on top of the piston and use a feeler guage where it over hangs the deck. Use the straight edge parallel with deck in the middle of piston(on the centerline)

If the rods are out of the motor they should measure close to 4.424"-4.426" from inside to inside:
http://www.dieselplace.com/forum/attachment.php?attachmentid=34941&stc=1&d=1172846227 (http://www.dieselplace.com/forum/attachment.php?attachmentid=34941&stc=1&d=1172846227)
[COLOR=red](Image has been resized. Click it for full size.)[/COLOR

well they are stock cummins rods but the have been strengthened and duramax are not.

How do they do that?

Calipers will work if you are experienced with them and are looking for .005" or more variation.

The wristpin bore is offset to the crank bore, and will give unreliable readings unless you hold the calipers perfectly square to the bores.

If anyone needs rods checked, I do this, for eye-to-eye distance within .0001", if you also want roundness of bores and parallelism also, I can do that as well. This is done with Mitutoyo Coordinate Measuring Machines that are calibrated to .00004" and referenced to NIST. They are done in a temperature controlled laboratory and include itemized hardcopy report. Results are guaranteed, and done on the same equipment we use for NASA and JPL work.

LBZ rods weigh a few grams more, and have slightly more metal in the beam. Perhaps 10% stronger if the alloy is the same.

How do they do that?I think they paint them with John Deere Green Paint:D :D

I think they paint them with John Deere Green Paint:D :D

Didn't think of that, I knew that Red paint made stuff weaker.....
:D:D

As a general rule of thumb what we have learned are some limits to go by on a properly tuned Duramax engine. LB7 & LLY motors are good for about 500 - 550 RwHp and the LBZ engine is good for about 550 - 600 RwHp. Beyond these numbers your playing with fire and the odds of getting burned are pretty high. Ric has taken it slow and easy and gotten lucky as his desire to check and recheck saved him. Had he just let it go because it ran OK it would have cost him big. He didn't have to share anything but he chose to do so, to try and help others save some from his experiences. So it up to each of us to decide to listen to what's been found and control what we do to our own projects.

PS - "Caliper" measure should be 4.418"

Factory rods are 163.000mm center to center and are typically less than .0004" eye to eye variation, or .01mm.

That is the value that my regular ol $80 pair of calipers came up with(4.426") measuring a stock motor LB7 Rod, a Crower rod with a year of use, and a brand spanking new R&R Rod. They were all within .001". (Taz's were 4.398")Most likely you'll be measuring protrusion as a complete disassemble wouldn't be necessary if they aren't shortened.

The fact is, a bent rod will be obvious, it has been posted over and over again, the horsepower limits. If you add a turbo, your rods will bend, if you add twin cp3's on top of a turbo they will really bend, and if you add big compound turbos, they will bend .090" in about 15 seconds and the crank will knock the bottoms of the pistons off:eek:. And OF COURSE, this is assuming you are pushing these components...

Steve sumed it up Nicely:
As a general rule of thumb what we have learned are some limits to go by on a properly tuned Duramax engine. LB7 & LLY motors are good for about 500 - 550 RwHp and the LBZ engine is good for about 550 - 600 RwHp. Beyond these numbers your playing with fire and the odds of getting burned are pretty high. Ric has taken it slow and easy and gotten lucky as his desire to check and recheck saved him. Had he just let it go because it ran OK it would have cost him big. He didn't have to share anything but he chose to do so, to try and help others save some from his experiences. So it up to each of us to decide to listen to what's been found and control what we do to our own projects.

I just wanted to add that I believe the total engine failures(rods attempting to escape the block) are due to continuing to drive an engine with shortened rods as it becomes quite out of balance as the rods don't always shorten at the same rate as each other.

I just wanted to add that I believe the total engine failures(rods attempting to escape the block) are due to continuing to drive an engine with shortened rods as it becomes quite out of balance as the rods don't always shorten at the same rate as each other.

Don't forget also that as the rod shortens, eventually the piston skirt hits the crank. :eek: ;)

I along with many others appreciate it when guys like Rick come out and let the rest of us know what is going on. Saves all of us time and money. I reported that I feared my LB7 had bent a rod. Smoking white at idle, balance rate especially on #8 had gone to +7. When we got the motor out and pulled the head it was not obvious, all the piston protrusions looked the same. There was carbon build up in #8 so we thought it may have been an injector issue. We won't know for sure untill the block is tore down and we get the report back on the injectos. But like Rich reported the truck was not makeing the power it should have. Track times were starting to slip a bit and it starting making a slight vibration it had not previously had. Might have been in my head but I decided to shut it down before I windowed the block. I'll report what the problem turns out to be once we know. Twin Turbos, Twin CPs big injectors, big lift pump and a hot tune. Was a LB7 but odds are pretty good we were asking for it as well.;)

PS - "Caliper" measure should be 4.418"

Factory rods are 163.000mm center to center and are typically less than .0004" eye to eye variation, or .01mm.

The Duramax center to center rod dimension is not 163.000" it is 163 mm +-.025mm which converters to 6.418 +-.001". Also the pin end and crank end bores have sizes and tolerances to them so the measurement by caliper will vary based upon adding all these together.

Suppose you explain to us all what the difference between 163.000mm and 163mm is? This should be great!

You need to get your rods from another source. Factory rods are ±0.010mm on all the samples I've seen.

At least wait until I'm wrong before you waste your time correcting me.

:eek: ..................:D

I'll leave the measuring to you guys..............:cool:

:eek: ..................:D

I'll leave the measuring to you guys..............:cool:

Good call Tony, it's hard to find those marks on the tape measure ):h

Suppose you explain to us all what the difference between 163.000mm and 163mm is? This should be great!

You need to get your rods from another source. Factory rods are ±0.010mm on all the samples I've seen.

At least wait until I'm wrong before you waste your time correcting me.

Calling a dimension out to 3 places pasted the decimal point Vs calling it the full number with nothing past the decimal place is different, and you should know that Also how many samples are we talking about here you have checked 1, 100, 1000 or is it more of your fuzzy math? The numbers I have given are how they are made by Isuzu if you chose not to believe it that's up to you.

Just so the rest of us can play along. These are the official #'s.

Connecting Rod Length
163.0 mm / 6.42 in

Connecting Rod Bore Diameter - Bearing End - Production Value
62.958-62.979 mm / 2.4789-2.4795 in

Connecting Rod Bore Diameter - Pin End - Service Limit
34.53 mm / 1.3594 in

Connecting Rod Bore Diameter - Pin End - Production Value
34.512-34.522 mm / 1.3587-1.3591 in

Connecting Rod Bore Diameter - Bearing End - Production Value
62.958-62.979 mm / 2.4789-2.4795 in


Rick

I believe this is wrong for the rod itself. I think that's the numbers for a rod with bearing installed.

Another good thread crashing and burning. Thanks fellas. You know who you are.

Rick

I believe this is wrong for the rod itself. I think that's the numbers for a rod with bearing installed.

Sorry, dealer mechanic didn't say and I didn't think to ask. He said those were straight out of SI.

OK you boys flip'em out on the table and we'll measure.:drop_mout :evillol:

Looking from space:

+
=============================================)
+

I think it should be more like this since it's a connecing rod thread:

O==o

:lol:

The Actual number is 67mm for the crankshaft end of the rod. The rest of the numbers in Rick's post are correct.

I've never been happy with GM's conversion from Metric to Imperial.
163mm = 6.417 if you carry it out to 3 places.

Using a rod that is 6.420 instead of 6.417 could mean your pistons are now sticking out of the block by an extra .003.

This means your 17.5 compression LB7 just became 17.71. :eek:

When I sign in, I get a little banner that says I ain't said chit in a while, so here's something to get rid of it.

Powder metal (PM) rods are fine for stock applications. Most people think that the powder process (and potential porosity) is the problem, but usually it isn't.

Dmax rods are pressed into a "green" compact and then hot forged. This densifies the compact and most of the time, it's 100% dense. If you cut it up, you may find a pore, but you'll spend a lot of time looking. And depending on where it is, it may not affect the part strength at all.

However, where the problem really lies is the requirements of fracture splitting.

For the big picture view, the vast majority of current auto con rods are fracture split. This saves a ton of machining and can reduce the cost of the rod by 30% or more (and is made much more quickly). The powder metal associations work very hard to push the technology further, and their industy consortiums will push until all rods are powder metal. It makes total sense for stock applications. Fracture splitting saves cost and makes a great joint. So what's not to like?

What's not to like is the alloy.

There was a big fight some time back between the powder rod people and the steel rod people. Steel companies want to sell forged metal rods, but they couldn't be competive against PM (because of later having to machine the cap surfaces). So they went and worked out an alloy that would fracture split like a PM rod. It came very close, but to make a long story short, it failed because of cost. Ingot metallurgy went to war with PM and got its butt handed to it because of cost.

So back to the alloy. It takes a specific composition of iron alloy to work well in a PM application for fracture splitting. There are a number of PM alloys out there, but the key point is this: the alloys being used for rods come nowehere near the properties of an high-strength ingot-metallurgy alloy like 4340 or its variants (which could never be fracture split because they're too strong). The main reason is, they don't have to. They're not going into F1 cars, for Pete's sake, so all they need to be is decently strong and be 100% repeatable when compacted, forged, and split.....with little yield loss.

The fact is, if the rods are bending in compression, we're simply exceeding the yield stress of the PM alloy. You can redesign the rod and put a bit more metal in the right place and help (LBZ rods), but again, you're nowhere near the yield stress levels that can be achieved in expensive ingot-metallurgy alloys.

Now, could you make a 4340 PM (or other high-alloy) rod? Maybe. But it probably wouldn't fracture split, so there would be no point in doing it vs. a ingot-metallurgy piece. So if you want 4340-level of strength, you have to suck it up and pay for all the yield losses from ingot to slab to plate, take all the machining time hit, and voila, you have a beautiful rod.

Make sense?

When I sign in, I get a little banner that says I ain't said chit in a while, so here's something to get rid of it.

Powder metal (PM) rods are fine for stock applications. Most people think that the powder process (and potential porosity) is the problem, but usually it isn't.

Dmax rods are pressed into a "green" compact and then hot forged. This densifies the compact and most of the time, it's 100% dense. If you cut it up, you may find a pore, but you'll spend a lot of time looking. And depending on where it is, it may not affect the part strength at all.

However, where the problem really lies is the requirements of fracture splitting.

For the big picture view, the vast majority of current auto con rods are fracture split. This saves a ton of machining and can reduce the cost of the rod by 30% or more (and is made much more quickly). The powder metal associations work very hard to push the technology further, and their industy consortiums will push until all rods are powder metal. It makes total sense for stock applications. Fracture splitting saves cost and makes a great joint. So what's not to like?

What's not to like is the alloy.

There was a big fight some time back between the powder rod people and the steel rod people. Steel companies want to sell forged metal rods, but they couldn't be competive against PM (because of later having to machine the cap surfaces). So they went and worked out an alloy that would fracture split like a PM rod. It came very close, but to make a long story short, it failed because of cost. Ingot metallurgy went to war with PM and got its butt handed to it because of cost.

So back to the alloy. It takes a specific composition of iron alloy to work well in a PM application for fracture splitting. There are a number of PM alloys out there, but the key point is this: the alloys being used for rods come nowehere near the properties of an high-strength ingot-metallurgy alloy like 4340 or its variants (which could never be fracture split because they're too strong). The main reason is, they don't have to. They're not going into F1 cars, for Pete's sake, so all they need to be is decently strong and be 100% repeatable when compacted, forged, and split.....with little yield loss.

The fact is, if the rods are bending in compression, we're simply exceeding the yield stress of the PM alloy. You can redesign the rod and put a bit more metal in the right place and help (LBZ rods), but again, you're nowhere near the yield stress levels that can be achieved in expensive ingot-metallurgy alloys.

Make sense?

What are stock Cummins rod's made from?

I believe they are forged ingot-metallurgy steel, but I don't think they're 4340.

So they'd be a step above what the OEM Dmax rod is, but not near what a 4340 rod would be. I understand 4340 rods are now being built for the CTD.

The stock CTD rod is also much larger in dimension, which helps. It's amazing that they can turn those parts as fast as some of 'em do. That thing is totally overdesigned for pickup use!

I believe they are forged ingot-metallurgy steel, but I don't think they're 4340.

So they'd be a step above what the OEM Dmax rod is, but not near what a 4340 rod would be. I understand 4340 rods are now being built for the CTD.

The stock CTD rod is also much larger in dimension, which helps. It's amazing that they can turn those parts as fast as some of 'em do. That thing is totally overdesigned for pickup use!

Thanks for the metalurgy lesson, Mat....that helped a lot toward understanding why the rods would bend at upper power levels.

No problemo.

To visualize why they bend, just get a skinny yardstick, stand it up on end, and apply a load.

The first thing is does is buckle. It's because its length is many times longer than the dimensions of its cross section. Get this, it's called a "slender column" in complicated engineer geekspeak.

Our conrods are doing the same thing when under load. They're trying to buckle to relieve the stress applied to them. For light loads, if they buckle a hair and stay under the yield stress, when unloaded, it goes back to the original shape. When you hit the cylinder pressure that causes the metal in the rod to yield, then you've got permanently bent rods.

As with the yardstick, the fibers on the convex side are in tension, and the fibers on the concave side are in compression. That's why the convex side splinters when you push too far. The conrod is similar, and although the metal doesn't have "fibers" like wood, you can visualize the stresses that way in your head.

The fact that the rods bend and usually don't break says that the PM metallurgy ain't totally crap....pretty impressive what they put up with.

One of our perspicacious *cough* members has pointed out that CR CTD have fracture-split rods. I went over to the TDR and found exactly ONE thread about it, and they agree.

Now again, this could be a ingot/billet forging that is fracture split, or a PM fracture split rod.

They'll be yanking their beards and rending their garments if they're PM, it's one of their bragging points and ragging (on us) points.

I'll check some more too.

When I sign in, I get a little banner that says I ain't said chit in a while, so here's something to get rid of it.


Wow I would say you just took care of that. 4 posts in the same thread in a day, Not a productive day at work eh?
There are aftermarket rods available for the cummins now. What haisleys suggested especially in a street class and I think even the superstreet type engine, is reuse the stock rods. Their feeling is you won't experience a manufacturing defect in the stock rod. Then just balance it. I would think a stock rod xrayed or whatever term used should indicate voids and what not. I recall Straley was running stockers in his superstreet truck at cynthiana. I think the rods handled the 7710 rpm, but the stock rod bolts did not.

we need a conversion kit, install Cummins rods in a Dmax...

its a V8 vs. an I6. The I6 is always going to be stronger regardless so stop blaming GM.


the big macv v8 in semi pullers hold up fine on stock rods so its not the V8 theroy

we need a conversion kit, install Cummins rods in a Dmax...

Can you imagine what the deck height would be? :D


Zstroken, that's my issue with the DP....I'm an addict....it's either hours on end, or nothing!

Can you imagine what the deck height would be? :D


Zstroken, that's my issue with the DP....I'm an addict....it's either hours on end, or nothing!


Not an issue, that is a condition I think. OCD :)

BOBO, Another good thread crashing and burning. Thanks fellas. You know who you are.
__________________

I would think a good thread would be one with a goal of accurate information, that way when someone reads something they can trust that its that its correct. And if they missprint something that could be misleading or confusing I dont think someone should get flamed for clarifying or correcting them. Its all part of the debate/quest for information. NOBODY IS RIGHT ALL THE TIME! Most of us members dont understand nor do we care about the personal vendetta's between the big tuners. Stop the constant bickering please!!

BOBO, Another good thread crashing and burning. Thanks fellas. You know who you are.
__________________

I would think a good thread would be one with a goal of accurate information, that way when someone reads something they can trust that its that its correct. And if they missprint something that could be misleading or confusing I dont think someone should get flamed for clarifying or correcting them. Its all part of the debate/quest for information. NOBODY IS RIGHT ALL THE TIME! Most of us members dont understand nor do we care about the personal vendetta's between the big tuners. Stop the constant bickering please!!

I'm somewhat of a lightning-rod for these situations, so I'll just stop posting in these kinds of threads. I had already cut way back. That should keep the peace.

There are aftermarket rods available for the cummins now.

why is there a need for these tho?

Mat- that was awesome, thanks for the long description. What exactly makes the cummins rods "invincible" to high power? Just the larger size of them? Or something else? Or...?

I'm somewhat of a lightning-rod for these situations, so I'll just stop posting in these kinds of threads. I had already cut way back. That should keep the peace.

I meant no offense to you personally, I hope you didnt take it that way.:o:
It was a general statement of frustration and worry that people would spend enough time bickering with everybody that people would quit posting there experiences/knowledge. But Im afraid it may be to late.

I meant no offense to you personally, I hope you didnt take it that way.:o:
It was a general statement of frustration and worry that people would spend enough time bickering with everybody that people would quit posting there experiences/knowledge. But Im afraid it may be to late.

No offense taken.

It was back on topic, lets not worry about it now. Just keep it on topic from here on out.

Great stuff Mat, thanks, hope there isn't a test later.:D

Cummins rods bend too. I've got 6 of them here that failed. So we've got a fix for those as well. The rod itself is much bigger than a Duramax rod and depending on the year model you have the rods are different but all the 24 valve motor have PM rods with cracked caps and the earlier ones have forged rods.