I was just thinking to myself...

hmm I havent really heard of any broken rods going out the side of the block recently. Yet every day the cracked piston deathtoll seems to double what it was the day before.

Everyone used to say "oh the rods are by far the weakest link and will go first", but it seems like in the last year, that trend is changing.

1 1/2 to 2 years ago it seemed like no one was cracking pistons, even though they were close to the same HP levels as today. No Limit and all the big HP on stock internals guys were lunching motors with rods through the side of the block, but there werent many cracked pistons. At least it didnt seem like it.

SO whats changed? Tuning? Different fuel? Hotter weather? Different oil? People are just running their trucks harder than ever?

Am I totally out to lunch or has anyone else noticed this too?

ben

I was just thinking to myself...

hmm I havent really heard of any broken rods going out the side of the block recently. Yet every day the cracked piston deathtoll seems to double what it was the day before.

Everyone used to say "oh the rods are by far the weakest link and will go first", but it seems like in the last year, that trend is changing.

1 1/2 to 2 years ago it seemed like no one was cracking pistons, even though they were close to the same HP levels as today. No Limit and all the big HP on stock internals guys were lunching motors with rods through the side of the block, but there werent many cracked pistons. At least it didnt seem like it.

SO whats changed? Tuning? Different fuel? Hotter weather? Different oil? People are just running their trucks harder than ever?

Am I totally out to lunch or has anyone else noticed this too?

ben

I have noticed rod to piston ratio has changed too. Which is nice as I'ld rather hone a cylinder or two vs. having a windowed block.

I don't think it's one factor that's done it, but a combination of the following:

Guys with older motors having already "been there....done that" with a broken rod, swapped out rods before they do break (proactive), or are taking it easier (learned from other people's mistakes).

Then there has been tuning changes and hopefully more to come as we are starting to look at chamber pressures real time.

The fact that the new motors are using a marginally stronger rod, and some think a "marginally weaker piston" may be a reason why rods are lasting a little longer. Even if the pistons are the same strength, the rods don't give as much and therefor is putting more stress on the pistons...

An now there are more Duramax trucks on the road than before and trucks are getting older and higher mileage....

The fact that the new motors are using a marginally stronger rod, and some think a "marginally weaker piston" may be a reason why rods are lasting a little longer. Even if the pistons are the same strength, the rods don't give as much and therefor is putting more stress on the pistons...


My thoughts also.

I've only heard of one LBZ that bent rods, and that was Tazman doing only God knows what to his engine. Seems like the rods are strong enough in the LBZ to handle high everyday HP.

My thoughts also.

I've only heard of one LBZ that bent rods, and that was Tazman doing only God knows what to his engine. Seems like the rods are strong enough in the LBZ to handle high everyday HP.

Tomac tried to run a stock LBZ short block. Bent the rods and cracked a piston.

Dual pumps, big single, and injectors must be a bit much for a stock blocked anything.

Dual pumps, big single, and injectors must be a bit much for a stock blocked anything.

X2

Most guys with the LB7's would have windowed the block with that combo (Bogger is one that comes to mind that did just that).

I was just thinking to myself...

hmm I havent really heard of any broken rods going out the side of the block recently. Yet every day the cracked piston deathtoll seems to double what it was the day before.

Everyone used to say "oh the rods are by far the weakest link and will go first", but it seems like in the last year, that trend is changing.

1 1/2 to 2 years ago it seemed like no one was cracking pistons, even though they were close to the same HP levels as today. No Limit and all the big HP on stock internals guys were lunching motors with rods through the side of the block, but there werent many cracked pistons. At least it didnt seem like it.

SO whats changed? Tuning? Different fuel? Hotter weather? Different oil? People are just running their trucks harder than ever?

Am I totally out to lunch or has anyone else noticed this too?

ben
Well the only thing different being burned through the motors from a few years ago is the fuel. I have no idea if the fuel burns at a different rate than before. I feel that the tunning has helped in keeping things alive longer as Nick shown with his pressure monitoring graphs and thats why I had Rob make my tune. There's not to many engines out there that you can double the power output from it's stock design and it can take that beating daily for long periods of time. Just my 2 cents.

The factory rods are a bit stonger in the LBZ and LMM

About 4 years ago I windowed my block then I replaced the motor and then cracked an lb7 piston. I replaced it with lbz cut pistons and crower rods. The lbz pistons lasted 3500 miles of everyday driving weekend towing and racing. Then the #1 piston cracked. I replaced the lbz with Ross pistons and have been driving it everyday and towing my boat on the weekends. I still race it every once in a while but have put the stock injectors back in. The ross pistons have about 15k miles on them.

How many people have cracked a piston with stock injectors? Its odd that some have trouble and some don't. I sure wish we had the answer. Jeff

How many people have cracked a piston with stock injectors? Its odd that some have trouble and some don't. I sure wish we had the answer. Jeff

I did, stock turbo, stock injectors running 500 hp tune daily for only 8K miles. Otherwise, I have had Juice with Attitude, Edge Evolution, Bully Dog PMT (all three beta testing) then PPE 160 hp tune or 70 hp EFI tow tune for the first 36K miles.

How about this. You guys that cracked pistons how much power was you making at the time and how was your tune set up as far as main injection timing?

Oh and also what was you doing at the time it broke?

Its EGT's and hot oil (lack of piston cooling) that kill them more than timing. I am very conservative with timing in all of my tunes.


just my oppinion.

Hmm I thought everyone had reached a consensus quite a while back that timing was doing it Ben? Obviously all parts have limits but I think some of the huge problem with lbz pistons is the quality control. I think some trucks just have faulty pistons from the get go and it doesn't take near as much to break them. What are your thoughts on the pcv reroute helping to save the pistons?

How many people have cracked a piston while actually racing or pulling? seems like a lot have been towing or messing around on the freeway/street?

Its EGT's and hot oil (lack of piston cooling) that kill them more than timing. just my oppinion.

Mine too.;)

Its EGT's and hot oil (lack of piston cooling) that kill them more than timing. I am very conservative with timing in all of my tunes.


just my oppinion.

I agree with your thoughts ben, but one hole in the theory; why wouldn't we see more LLY's cracking pistons than the others? I think the LLY is the one with the most heat problems and thus the largest piston cooling issues due to lack of oil pressure...

Ive seen 3 trucks this year with low timing and low EGTs all with cracked pistons
All 3 trucks had less than 28 at 3000 rpm and lower than 1350 EGTS

I agree with your thoughts ben, but one hole in the theory; why wouldn't we see more LLY's cracking pistons than the others? I think the LLY is the one with the most heat problems and thus the largest piston cooling issues due to lack of oil pressure...
I'm sure the heat and low oil pressure plays a part of it but you see more guys with piston failing on the street than during sled pulls that I see anyways. Difference with sled pulls is they are up in rpms and the motor dosen't get pulled down in rpm during shifts as many times. But they tend to run higher egts and everything gets hot and oil pressure goes down. From what I've read most have let go in the mid 2000 rpm range on the street. Just thinking out loud not trying to say who's right or wrong but the more we talk about it I feel the more we might get it figured out sometime.

I'm thinking of the ones that make around 500 rwhp.

Well whats wierd regarding oil pressure, is the new engine has lower than stock highway-cruise oil pressure (one or two tick below 60), yet hot idle oil pressure is higher than the stock original engine. (19-20)

original engine had like 17ish hot at idle in the summer, and was right at the 60psi mark in cruise on the highway.

Maybe looser tolerances with a block that has 300k miles on it? I dunno. The oil pressure in cruise doesnt worry me really, theres lots of air moving through the stack, and theres boost going into the engine, so everything is moving around/cooling more efficently. Racing or towing heavy, and getting right off the offramp and going right down to idle the pistons must just get the crap beat (heatsoaked) out of them.

Another reason I always run the truck in tow/haul, and getting off offramps If ive been towing or running the engine hard on the highway, ill manually put it in 3rd do force a downshift and rev the engine way up. IMO this helps the engine cool off and proabbly be easier on the hot pistons that are fragile enough as-is. Because if you do that, the engine is in DFCO mode (no fuel injected), and its revving high unloaded, which moves lots of air across the engine (fan), circulates coolant faster thru the engine (which helps cool the oil) keeps the oil pressure up high so it can circulate fast thru the motor and wick as much heat away from the pistons as possible before you come down to idle where the oil pressure drops off "like a rock".

Our pistons just dont have the mass that the cummins pistons do, thats why ours are more prone to cracking under high hp/load/heat/performance applications. Obviously the more mass the pistons have the easier they dissapate heat and can take a LOT more heat without stressing and cracking. Because our pistons have smaller mass and therefore less self-cooling ability, proper oil pressure/temperature is critical. Im almost inclined to say as far as fluids go, the oil cooling necessity may be more important the coolant cooling.

ALMOST all the time, when the pistons get that "hole" taken out in the inside lip of the reentrant bowl where the crack starts, its on the opposite side of the oil cooling entry passage. I am VERY interested to see what (if anything) GM has changed as far as piston design/cooling/oil flow architecture for the 2010 duramax. With projected HP at 400+ at the same 6.6 liters displacment, there is enough fuel for a given CID to create potential EGT issues with a heavy trailer and a driver who doesnt care or have an EGT gauge. (which, he shouldnt have to care, he should be able to go WOT and drive normally and not have to install and watch gauges on a stock truck). Im guessing redesigned pistons and different oil cooling system. On top of the obvious turbo(s) update/replacement. GM knows what we are doing with these engines, and obviously frowns upon us and blames us when things DO fail.....BUT. In reality, they should be thanking us because WE (dmax hotrodders) are theyre best real world test subjects. SO they look at what we are doing, and because we are at such high power levels, we reveal all of the weak links for GM in severe abuse applications. Sure, pistons for the most part wont crack at stock power levels, BUT at high power levels they are one of the weakest links....so GM looks at this and says OK so these guys are running stupid power levels and the common failure is cracked pistons. So now we know that the next subject of redesign on the drawing board is pistons. These guys at 1000rwhp arent breaking blocks, so we know we have a winning formula there, so we dont have to spned money on R&D'ing a new one when we can plainly see in SEVERE applications, its still holding up fine.

ok im rambling on, but you guys can see what I m trying to say.

OR....we could just all do twins, keep EGT's low, problem solved IMO.

ben

From what I've read most have let go in the mid 2000 rpm range on the street.

:exactly:

funny how it works. You beat the absolute crap out if it all day on the dyno, make a bunch of runs at the track or hooks to the sled, run the engine all out balls to the wall, and it runs like a champ...




...and then blows up the next day as you are pulling away from a stoplight in town after coming back from getting food or something.


:wtf:

:exactly:

funny how it works. You beat the absolute crap out if it all day on the dyno, make a bunch of runs at the track or hooks to the sled, run the engine all out balls to the wall, and it runs like a champ...




...and then blows up the next day as you are pulling away from a stoplight in town after coming back from getting food or something.


:wtf:

Mine cracked at idle, remote started it, walked out 5 minutes later so I could have cold AC...

:exactly:

funny how it works. You beat the absolute crap out if it all day on the dyno, make a bunch of runs at the track or hooks to the sled, run the engine all out balls to the wall, and it runs like a champ...




...and then blows up the next day as you are pulling away from a stoplight in town after coming back from getting food or something.


:wtf:
Yeah this is what baffels me. Beat the crap out of it but don't get on it from a stop light cause you might break it:wtf:In your previous post I do agree about the piston mass and trying to keep them cool as you can. I like the twins idea and it does seem that if you have them to a certain point your safe. To bad gm won't come out with a compounded setup from the factory.

To bad gm won't come out with a compounded setup from the factory.

we'll just have to see what 2010 holds for us... :)

400HP, twin turbo, 8 speed allison. 2010 sounds like a good year!

400HP, twin turbo, 8 speed allison. 2010 sounds like a good year!

Yes it does! It will be time for a new truck by then too lol:D

Well if that's all true guess I'm done spending money on this one:rolleyes:

OR....we could just all do twins, keep EGT's low, problem solved IMO.

ben

Could also get DPR oil pump:D

Ben there is more than one truck with twins and low EGTS with cracked pistons:(

Could also get DPR oil pump:D

Ben there is more than one truck with twins and low EGTS with cracked pistons:(


I know Nasty was one, but she can't really be counted as she was in a league of her own considering the HP/TQ output. Of the one's you speak about, are there any that were in the 550RWHP range that broke a piston. Also, how long of a life did they have with a single charger and at what ouput.

One thing I've been curious about is shift defuel (or lack thereof). It's hard on the transmission as clutches are engaging/disengaging and I imagine it's got to be tough on pistons as well. You are turning a decent RPM and fueling it well, but then all of a sudden the transmission shifts and the engine RPM goes down quickly and you are still putting the fuel to it, that's got to be torturous for the pistons.

Has anybody lost a piston at 550RWHP or less and ONLY run tunes with a fair amount of defuel?

Right now I have several EFI live tunes, but I am only planning to stick with the ones with defuel. It sucks when it shifts, but I (crossing fingers) hoping it will help save the transmission (even though it's built) AND the stock internals.

Some day when my payments stop, I would like to build the bottom end and not have to worry about it as much, but I can't do it now.

Has anyone logged cylinder pressures before and after shifts (1-2, 2-3, 3-4, 4-5, 5-4, 4-3, 3-2, 2-1) with and without defuel, to see what effect it has on CP? I'm willing to bet without defuel, CP's will spike tremendously.....

What if any are the chances of fuel temp play a part, hot piston and significantlly cooler fuel, could cause extra stress on the piston bowl.

I only know of one twin LBZ that broke a piston. Truck has been used hard and he is a good tuner did his own tuning with EFI.

Sweetdiesel, what trucks are you mentioning, you can PM if needed. I'd be surprized to hear of more since I tune most of the MPI twin LBZ's and I have yet to hear of any of my customers losing a motor.

I only know of one twin LBZ that broke a piston. Truck has been used hard and he is a good tuner did his own tuning with EFI.He is a good tuner :)

Sweetdiesel, what trucks are you mentioning, you can PM if needed. I'd be surprized to hear of more since I tune most of the MPI twin LBZ's and I have yet to hear of any of my customers losing a motor.

Rob
the one truck you know of and the other was not a MPI twin setup,however im sure you have heard of the member
Im not bashing twins in any way,Im just not convinced on the low timing and low EGTs therory as the be all end all......Im sure it dont hurt having low EGTs:D

Mine cracked at idle, remote started it, walked out 5 minutes later so I could have cold AC...


So thats a remote detonation?:D

I share the belief that EGT's and timing plays a major role. I would add that temp cycling also plays a role in higher milege lower power level engines.

Along those lines, wouldn't a truck running lower timing with a water injection system be a good/cost effective alternative for those of us that don't want to run twins?

Has anybody lost a piston at 550RWHP or less and ONLY run tunes with a fair amount of defuel?

Right now I have several EFI live tunes, but I am only planning to stick with the ones with defuel. It sucks when it shifts, but I (crossing fingers) hoping it will help save the transmission (even though it's built) AND the stock internals.

Some day when my payments stop, I would like to build the bottom end and not have to worry about it as much, but I can't do it now.

Has anyone logged cylinder pressures before and after shifts (1-2, 2-3, 3-4, 4-5, 5-4, 4-3, 3-2, 2-1) with and without defuel, to see what effect it has on CP? I'm willing to bet without defuel, CP's will spike tremendously.....

Rick Lance has broken at least one piston and was never over ~400 HP

Hot chamber, pressures come up a fair bit on the shift with defuel. I have not logged it without defuel. A hot chamber is like adding timing Cylinder Pressure wise.

Of the one's you speak about, are there any that were in the 550RWHP range that broke a piston.Yes, the LBZ he was talking about was running a tune in the 550 HP range when it broke. Also, how long of a life did they have with a single charger and at what ouput.Approx. 10,000 miles stock. Approx. 10,000 miles with an Edge Juice. Approx. 20,000 with EFI tunes ranging from 50 (not often) to 500 (most often) horsepower. Approx. 7,000 miles with twins and big tunes.

How many people have cracked a piston with stock injectors? Its odd that some have trouble and some don't. I sure wish we had the answer. Jeff


I was stock injectors and cracked #6 and #3 was starting to get a white lean look to it.

What do you think of it having to do with fuel, how many of you that have lost a piston ran addative? It seems like this all hit the fan after the LBZ came out and people started modding them. It's not just the LBZ that is loosing pistons, it is just when the majority of failures showed up. This is also the same time frame we were forced to start using ULSD fuel. What I am getting at is, in most cases its just one piston that failed, not numerous, as possibly to indicate a injector malfunction(sticking open,ect). It has also happened to stock trucks as well. Could it be the ULSD's lack of lube in the injector? Don't know if this is a viable therory, but I was just thinking at work today, and this hit me.

Rick Lance has broken at least one piston and was never over ~400 HP


4 to be exact, and one that had been run over 400 hp. :(

Rick Lance has broken at least one piston and was never over ~400 HP

Hot chamber, pressures come up a fair bit on the shift with defuel. I have not logged it without defuel. A hot chamber is like adding timing Cylinder Pressure wise.


wait im confused....so less defuel is perhaps better for the pistons???

So thats a remote detonation?:D

Yup :shootself :D

wait im confused....so less defuel is perhaps better for the pistons???

I don't think so, but I have not monitored CP for no defuel.

I don't think so, but I have not monitored CP for no defuel.
When I ran my ppe with the defuel turned on my egts where higher than when it was off. Seems like it would be the other way around but wasn't.

What do you think of it having to do with fuel, how many of you that have lost a piston ran addative? It seems like this all hit the fan after the LBZ came out and people started modding them. It's not just the LBZ that is loosing pistons, it is just when the majority of failures showed up. This is also the same time frame we were forced to start using ULSD fuel. What I am getting at is, in most cases its just one piston that failed, not numerous, as possibly to indicate a injector malfunction(sticking open,ect). It has also happened to stock trucks as well. Could it be the ULSD's lack of lube in the injector? Don't know if this is a viable therory, but I was just thinking at work today, and this hit me.
I've wondered the same thing and wonder if it burns any different than the old style fuel.

What do you think of it having to do with fuel, how many of you that have lost a piston ran addative? It seems like this all hit the fan after the LBZ came out and people started modding them. It's not just the LBZ that is loosing pistons, it is just when the majority of failures showed up. This is also the same time frame we were forced to start using ULSD fuel. What I am getting at is, in most cases its just one piston that failed, not numerous, as possibly to indicate a injector malfunction(sticking open,ect). It has also happened to stock trucks as well. Could it be the ULSD's lack of lube in the injector? Don't know if this is a viable therory, but I was just thinking at work today, and this hit me.

Dont run ULSD in Canada and we still blow and crack pistons:D

If heat is main and contributing factor why is only one piston failing in most trucks, instead of numerous piston in the same trucks. I know there have been a few with multiple failures, but the majority only one piston failure.

didnt mcrat burn all 8 at once melted them i thought?high egts i know that.but this was awile ago i could be screwing the pouch here.

didnt mcrat burn all 8 at once melted them i thought?high egts i know that.but this was awile ago i could be screwing the pouch here.

I believe he did and I "think" it was BMDmax who has SEVERE erosion on all pistons but none were cracked (if memory serves me). So EGT's alone aren't killing these pistons.

The sad part is, it is probably a combination of factors, and if one of those factors is poor quality control (piston to piston differences), we will probably be chasing our tail trying to find out what exactly causes piston failures at different HP levels.

Just thinking out loud here, but if my experience with welding, cutting, bending and beating on different types metal says anything, heat almost always seems to make metal more malleable, in that it tends to bend and deform rather than break or crack. Where I see cracks or breaks is when there is a rapid temperature change or just plain too cold for the stress it is getting, as in, the hot part will bend, the cold part will break.
Mine had enough long steady heat pulling heavy in the summer to lightly erode the surface of the heads (pistons showed no sign of it) and yet it lived.
Then a piston failed after lots of easy winter time driving, got on it one time just when the water temp reached normal, so I know the pistons were not hot, nor had they been for several months.
Do these circumstances give any clues, or am I thinking too far outside the box?:think:

Just thinking out loud here, but if my experience with welding, cutting, bending and beating on different types metal says anything, heat almost always seems to make metal more malleable, in that it tends to bend and deform rather than break or crack. Where I see cracks or breaks is when there is a rapid temperature change or just plain too cold for the stress it is getting, as in, the hot part will bend, the cold part will break.
Mine had enough long steady heat pulling heavy in the summer to lightly erode the surface of the heads (pistons showed no sign of it) and yet it lived.
Then a piston failed after lots of easy winter time driving, got on it one time just when the water temp reached normal, so I know the pistons were not hot, nor had they been for several months.
Do these circumstances give any clues, or am I thinking too far outside the box?:think:

With that theory, if you were cracking pistions with the cold air, would'nt it make sense to see more than one cracked pistion with the cold air being introduced to all cylinders?

What are some of the ambient temps when some of you guys cracked pistions and your obvoious killers were in check, such as sweet diesels 3 trucks with low timing and low egts around 3k rpm.

Ben,

with your idea of the oil being too hot and possibly being the detriment esp. mixed with the low oil pressure in the LLY, (not sure about the newer engines), I wonder how are guys with an oil coolers running 400-500hp tunes fairing? Could something this simple be a life saver for pistions.

How many guys out there lost pistions with oil coolers?

My .02

Marc

With that theory, if you were cracking pistions with the cold air, would'nt it make sense to see more than one cracked pistion with the cold air being introduced to all cylinders?
Marc

Most of us stop when something breaks, so unless every piston breaks at the exact same time, we probably won't know that.

My thought was not so much the cold air, as the cold/cool piston.
The air temp affects the piston temp only in a very small time frame before the compression starts to heat things up.
The oil on the other hand spends a lot of time in liquid contact with the whole bottom side, plus in the cooling channel in the piston thus having a big impact on it's temperature.
My question is,
Are there more pistons breaking when the piston and oil are both very thoroughly heated ?,
or when the piston and oil are barely warmed up?

would'nt it make sense to see more than one cracked pistion with the cold air being introduced to all cylinders?

I did 5 at once.

1 at a time for me. I've also just replaced the cracked piston in one and put it back on the road. It's still going.

1 at a time for me. I've also just replaced the cracked piston in one and put it back on the road. It's still going.


What did you have to do to the cykinder walls ?

We got lucky and caught it before it messed up the cylinder. Just honed it lightly, cleaned it, and put it back together.

Maybe there is a pattern....? I could be out in left field but maybe we could see a correlation. If we see engines that were in realative terms like EGT's, Timing, ect when it happened the other factors would be enlightening to compare if there is some sort of pattern. EG, some guys will say i was at operating temp, but when your ECT is up at 190-200 doesnt mean your oil is there, i think with these things in mind, others may or may not have similar conditions.

I understand its impossible to get all from everyone.......but heres an idea.
----------------------------------------------------------
How many pistions you cracked:

type of engine:

Miles:

Engine Coolant temp:

Oil Temp (running all day it was up to normal, or for example, running only 15 min):

Tranny Temp:

EGT's:

Timing:

Ambient temp: or dead winter, scorching hot summer etc:

Dragracing, Sled pulling, on the street, iding in my driveway etc:

loaded, unloaded:

RPMS, idling:

normal driving, beating it into next week:

speed:

Additional Failures (like injector sticking, over rev, etc):

est. HP of tune at the time:

Any Aftermarket Internals:

How you were treating the engine for the previous 15 minutes before it blew up?

I know is a shitload of info, but I think it would be cool to find all this out from you guys that did grenade a pistion. If i missed some valuble info:think:, include it and tell us what did your piston in.

Maybe there is a pattern....? I could be out in left field but maybe we could see a correlation. If we see engines that were in realative terms like EGT's, Timing, ect when it happened the other factors would be enlightening to compare if there is some sort of pattern. EG, some guys will say i was at operating temp, but when your ECT is up at 190-200 doesnt mean your oil is there, i think with these things in mind, others may or may not have similar conditions.

I understand its impossible to get all from everyone.......but heres an idea.
----------------------------------------------------------
How many pistions you cracked:

type of engine:

Miles:

Engine Coolant temp:

Oil Temp (running all day it was up to normal, or for example, running only 15 min):

Tranny Temp:

EGT's:

Timing:

Ambient temp: or dead winter, scorching hot summer etc:

Dragracing, Sled pulling, on the street, iding in my driveway etc:

loaded, unloaded:

RPMS, idling:

normal driving, beating it into next week:

speed:

Additional Failures (like injector sticking, over rev, etc):

est. HP of tune at the time:

Any Aftermarket Internals:

How you were treating the engine for the previous 15 minutes before it blew up?

I know is a shitload of info, but I think it would be cool to find all this out from you guys that did grenade a pistion. If i missed some valuble info:think:, include it and tell us what did your piston in.
I like the list and I hope I never have to fill it out... I would also add:

What were the EGT's when it happened and what EGT's has the truck seen over it's lifetime (i.e. truck has seen 1700° 4 times while dragracing/dyno pulls) If the truck wasn't at it's high EGT mark when failure occured, how long ago was the most recent high EGT?
Also, was the truck in a shift. I've heard several mentions of the truck in the middle of a shift when the piston popped.

How many pistions you cracked:1 #8

type of engine: lb7

Miles:62k

Engine Coolant temp: normal on the gauge 210 or watever it is

Oil Temp (running all day it was up to normal, or for example, running only 15 min):running for abuot 30 min so should have been atleast normal dont have a gauge though

Tranny Temp:200 about

EGT's:900-1100

Timing:not sure

Ambient temp: or dead winter, scorching hot summer etc:about 95

Dragracing, Sled pulling, on the street, iding in my driveway etc:towing a grade

loaded, unloaded: loaded 6000-7500

RPMS, idling:2500

normal driving, beating it into next week:normal driving

speed:65

Additional Failures (like injector sticking, over rev, etc):none

est. HP of tune at the time: ppe hot 2 et set on level 3 but i pretty much ran it on the highest setting everyday only turned it down when towing lol

Any Aftermarket Internals:none at the time
well there is all the information i have to start things off

Tomac tried to run a stock LBZ short block. Bent the rods and cracked a piston.


The LBZ rods were only bent a little bit :D and not causing any harm when a LBZ piston cracked

That setup was making 700 rwhp on Kennedy's Superflow

Good information here. Keep it coming, and I agree hopefully I wont have to fill out that list there also.

Like this?
Maybe there is a pattern....? I could be out in left field but maybe we could see a correlation. If we see engines that were in realative terms like EGT's, Timing, ect when it happened the other factors would be enlightening to compare if there is some sort of pattern. EG, some guys will say i was at operating temp, but when your ECT is up at 190-200 doesnt mean your oil is there, i think with these things in mind, others may or may not have similar conditions.

I understand its impossible to get all from everyone.......but heres an idea.
----------------------------------------------------------
How many pistions you cracked:1, #3

type of engine:LBZ

Miles:21,000

Engine Coolant temp:190

Oil Temp (running all day it was up to normal, or for example, running only 15 min):Had been run barely long enough to bring water temp to normal

Tranny Temp:Very cool yet

EGT's:Not sure exact but prob 1350 and climbing

Timing:25.4

Ambient temp: or dead winter, scorching hot summer etc:71 degree day

Dragracing, Sled pulling, on the street, iding in my driveway etc:Back country rd.

loaded, unloaded:Unloaded

RPMS, idling:2466

normal driving, beating it into next week:Normal driving for me, little extra punch before slowing for my driveway

speed:2466 rpm in fifth gear:D

Additional Failures (like injector sticking, over rev, etc):none

est. HP of tune at the time:500?

Any Aftermarket Internals:Stock

How you were treating the engine for the previous 8-10 minutes before it blew up? Driving it very easy to McDonalds-to-Go and letting it get warmed up from a cold start

Main Fuel Shot: 3250us

Turbo Boost: 37

I believe he did and I "think" it was BMDmax who has SEVERE erosion on all pistons but none were cracked (if memory serves me). So EGT's alone aren't killing these pistons.

The sad part is, it is probably a combination of factors, and if one of those factors is poor quality control (piston to piston differences), we will probably be chasing our tail trying to find out what exactly causes piston failures at different HP levels.

I severly melted / eroded four and split one all the way through inducing my failure. The other three had cracks as well.

The only bent rod was on the piston that fully split, I am sure the extra stress from trying to move the mess that was the piston in the cylinder did that.

had anyone other than brandon found cracked pistons upon diaassembly?

4 cracked pistons on the skirt. all on the drivers side. never noticed a problem except for the several injector cups that pushed

I pulled the following quote from Steve off the "old piston thread". Has the part I highlighted and bolded ever been expanded on? Or was this only in reference to modded LBZ pistons? I was curious if they found a machining glitch in factory pistons.


[QUOTE]I would guess its all up to where you want to spend the money. For me I've got a heavy foot and I say 100 Hp adder is fine but then I get use to it then it turn it up some more. So if you have better self control you might be fine with the LBZ rods, but at this point no one knows what they will hold for sure. We do know the LB7 rods fail around 500 -550 RwHp of prolonged use. I do not know what it would cost to buy factory LBZ rods but a set of our billet rods are $2750 so you can compare cost from that. If you switch to the LBZ piston you also need to switch the wrist pin as it takes a different pin than the LB7 piston. The LBZ piston is stronger as it is reinforced in the pin area and has a slightly lower compression rate to start with which is good for those of us with a heavy foot. If you would like a second opinion on the strength issue maybe MMS will chime in. The LBZ piston failures have been tracked down and it was not a piston problem but a machining problem with what was done to them. So until I see a problem I'm sticking with the LBZ units.[QUOTE]

Maybe there is a pattern....? I could be out in left field but maybe we could see a correlation. If we see engines that were in realative terms like EGT's, Timing, ect when it happened the other factors would be enlightening to compare if there is some sort of pattern. EG, some guys will say i was at operating temp, but when your ECT is up at 190-200 doesnt mean your oil is there, i think with these things in mind, others may or may not have similar conditions.

I understand its impossible to get all from everyone.......but heres an idea.
----------------------------------------------------------
How many pistions you cracked: 1

type of engine:06 LBZ

Miles: 44,000 and change

Engine Coolant temp: 100*

Oil Temp (running all day it was up to normal, or for example, running only 15 min): 100*

Tranny Temp:100*

EGT's:300*

Timing:tune had 27* max

Ambient temp: or dead winter, scorching hot summer etc: 100*

Dragracing, Sled pulling, on the street, iding in my driveway etc: idling in front of my shop

loaded, unloaded:unloaded

RPMS, idling: ~700 rpm

normal driving, beating it into next week: Idling

speed:0mph

Additional Failures (like injector sticking, over rev, etc):none

est. HP of tune at the time:500

Any Aftermarket Internals:none

How you were treating the engine for the previous 15 minutes before it blew up? I believe the words out of my brothers mouth was your truck is FAST!

I know is a shitload of info, but I think it would be cool to find all this out from you guys that did grenade a pistion. If i missed some valuble info:think:, include it and tell us what did your piston in.

...

...
So you had just got done running your truck hard and it was idleing in park at the time?

I know EGT's at the time were ~300°, but what EGT temps had the truck seen prior?

thanks,

So you had just got done running your truck hard and it was idleing in park at the time?

I know EGT's at the time were ~300°, but what EGT temps had the truck seen prior?

thanks,

I believe earlier in the thread he said he had just started the truck via remote, so it must have completely cooled down from his last fast ride:D

So you had just got done running your truck hard and it was idleing in park at the time?

I know EGT's at the time were ~300°, but what EGT temps had the truck seen prior?

thanks,

The problem is I don't know...My brother was driving my truck and the last words out of his mouth was "your truck is FAST!" So I am supposing it got hot, but just FYI, I only ever saw 1500 at the end of the quarter running the same tune.

Chad, when did this happen, and what tunning were you running. Feel free to PM me if you dont want to post it on the board.

Chad, when did this happen, and what tunning were you running. Feel free to PM me if you dont want to post it on the board.

No hiding anything, it happened 3 weeks ago and Nicks 530 rwhp tune was in the truck when it happened. That tune is 27* max timing.

Man I am sorry to hear about this. It seems like yours is a weird occurance since it happened at idle. I have been worried about this all along. I am addicted to the power, and I just ended up buying a car so I have something to drive if things go wrong when I put the twins on. It doesnt seam like there is much rhyme or reason to why this is happening. I have seen a lot of people running different tuning with similiar results.

There is very few tunners out there that have yet to have an occurence with cracking the piston. And of those few tuners even less have a sizable amount of people running there tunes.

Chad have you had a chance to tear into your block? Did it damage anything else? What does the future of your truck look like now?

There is very few tunners out there that have yet to have an occurence with cracking the piston. And of those few tuners even less have a sizable amount of people running there tunes.

Chad have you had a chance to tear into your block? Did it damage anything else? What does the future of your truck look like now?

Been to busy around here the last few weeks to pull it all the way down. We have been pulling the top of the motor off, have all the injectors out, egr off and what not. Tomorrow the heads should be off though, I will post pics of the damage next week when I get back from Weekend on the Edge. I have a motor coming from Texas, stock pull out for now and I will build the blown one over the next year into a competition build.

Been to busy around here the last few weeks to pull it all the way down. We have been pulling the top of the motor off, have all the injectors out, egr off and what not. Tomorrow the heads should be off though, I will post pics of the damage next week when I get back from Weekend on the Edge. I have a motor coming from Texas, stock pull out for now and I will build the blown one over the next year into a competition build.


Sorry your dealing with this but in the end it sounds like you will have a bad ass truck. Are you just going to run mild tuning until you get a motor built than?

No hiding anything, it happened 3 weeks ago and Nicks 530 rwhp tune was in the truck when it happened. That tune is 27* max timing.
I know max timing is important but these things seem to let go around 2000-2400 rpm range so timing there would be important also. Not saying this happend but is it possible when your brother drove it it let go while he was driving??? Seems odd to break during start up or idle unless the crack already started to form and broke through. Either way it sucks. Thanks for sharing your information!!

Sorry your dealing with this but in the end it sounds like you will have a bad ass truck. Are you just going to run mild tuning until you get a motor built than?

Yup, mild tow tuning until the new motor is built. My trucks racing career is on hold. Got any Fireman jobs open up there, I need a raise:D

I know max timing is important but these things seem to let go around 2000-2400 rpm range so timing there would be important also. Not saying this happend but is it possible when your brother drove it it let go while he was driving??? Seems odd to break during start up or idle unless the crack already started to form and broke through. Either way it sucks. Thanks for sharing your information!!

Steve, I saw the truck roll into the parking lot from my desk, it was not smoking at all. I have talked to a few people and this isn't the first time it has happened this way, damage caused earlier in the day, fire it up and bam. The truck had sat for 4 hours prior to me starting it...

Steve, I saw the truck roll into the parking lot from my desk, it was not smoking at all. I have talked to a few people and this isn't the first time it has happened this way, damage caused earlier in the day, fire it up and bam. The truck had sat for 4 hours prior to me starting it...
Thanks for sharing and not taking my post the wrong way. After reading what I typed and how I did it I myself thought it could be taken the wrong way. Sometime I don't type out what I'm trying to say how i would say it in person.

Yup, mild tow tuning until the new motor is built. My trucks racing career is on hold. Got any Fireman jobs open up there, I need a raise:D


Hahaha we have some new positions opening shortly. Its only as lucrative as you want to make it though.

I know max timing is important but these things seem to let go around 2000-2400 rpm range so timing there would be important also. Not saying this happend but is it possible when your brother drove it it let go while he was driving??? Seems odd to break during start up or idle unless the crack already started to form and broke through. Either way it sucks. Thanks for sharing your information!!


2000 - 2400 is where the max Chamber pressures tend to occur.

I am scared :D

when mike L rebuilt my tranny he was telling me about the oil squirters on the bottom of the pistons and he said something like they were activated by oil pressure like a certain pressure and then they would start spraying. does anyone know what that pressure is? maybe driving in tow/haul is a good thing if it keeps the squirters open the whole time you are slowing down. i have a turbo timer that runs my truck for two min after i take the key out so if i put my truck in high idle when hot for that two minutes will oil be sqirting on the bottom of my pistons that 2 minutes?

I think 24psi is when they shut off. Could be wrong though.

ben

Piston Cooling Jet Valve Opening Pressure196 KPa
29 psi

Piston Cooling Jet Valve Opening Pressure196 KPa
29 psi


Which means mine are NOT squirting at idle. My oil pressure at idle is 28 psi running 5w40 synthetic oil...

so does anyone think the lack off cooling oil on the bottom of the piston at idle rpm might be a factor in the cracking of pistons. if so then im putting some lucas in my amsoil to keep the pressure up.

Which means mine are NOT squirting at idle. My oil pressure at idle is 28 psi running 5w40 synthetic oil...



How much oil psi are the squirters seeing when you have 28psi at wherever your reading it from?

so does anyone think the lack off cooling oil on the bottom of the piston at idle rpm might be a factor in the cracking of pistons. .



yep


sorry about the incorrect spec I gave for the piston oil squirters, I was thinking it was 24 for some reason. :o:

http://www.dieselplace.com/forum/showthread.php?t=151060&highlight=oil+squirters&page=18



Read post 175

thanks addison that was the one I was looking for


Still though, there is lot LESS piston oil cooling at idle. Not to mention that the oil is not flowing through the oil cooler as quickly or as efficently. You beat the crap out of the motor, then suddenly bring it down to idle and it "shock heats" it.

thanks addison that was the one I was looking for


Still though, there is lot LESS piston oil cooling at idle. Not to mention that the oil is not flowing through the oil cooler as quickly or as efficently. You beat the crap out of the motor, then suddenly bring it down to idle and it "shock heats" it.


just ??maybe?? explaining why so many motors let go "after" the race/pull and not while the engine is opened up all the way....

thats an uneducated guess on my part.

obviously, not incited by a one time incident, but after multiple passes/pulls, and multiple numbers of heat/cooling cycles, the piston finally lets go after the truck is allowed to idle or at least unload the motor to the point where the pistons are no longer recieving the amount of oil squirter cooling needed to keep the pistons from turnin into a heat sinc.

i'm not a engineer, so i'll leave it at that.

I'm no engineer either but I all ways thought if you super heated anything casted then cooled it too fast you could cause it to crack because it becomes britle during cooling??

What about the hardening process during casting??? Dosen't it make it stronger but can it also make it more prone to cracking? Just thinking out loud.