LB7: Pistons ?

[NemesisDP]

When I talked to Wade when the PPE hot+2ET came out he said to be very carefull because they had had alot of LBZ's in with piston failers, but he also said that they had seen LBZ's that had pistons that looked like new after running the PPE HOT+2. Someone had told me that the earlier LBZ's had to have the wrist pins pressed in because they were to tight of fit and thats why they were cracking easier. I have ran both my LBZ's to 1600 + degs and no failer yet. 56,000 and 49,000 miles. Both with the PPE HOT+2.

My 02 has LB7 deliped pistons and has seen 1800+ deg in the quarter with no problems yet. When I bought the truck I was told it had dynoed 700 plus. Will pull the injestors soon and see if the bore scope we have at work will fit to look at the pistons.

 

[Turbotug]

Did I put cool and cooler in there enough?

 

[slowlmm]

I put a hole in my #7 piston at the track at the end of a 1/8th mile pass no crack just a hole. 600ish hp range and 1600 egt pass. my truck went 56,000 miles dual fuelers and the same race tune daily driven.

 

[JoshH]

You are running your gauge pre-cooler. What was your reason for putting it there? You are also running an external cooler, correct? If you had your gauge before you added the cooler, what kind of benefits did you see from it?

 

[Turbotug]

I installed my guage before I had the cooler. I would see average temps of 220+ just cruising around town. Put a small load behind it (or a bit of racing) and it would easily be 250+. When I decided to install the HTT I wanted some safety, being that it's only cooling is from oil, so I got the oil cooler too. Now my average around town temps are usually under 200, and even with my 37' toyhauler in tow I have to really work it to reach 240. Normal towing temps are 220ish with ambient temp in the 70s..

One thing that the cooler oil helped is the psi. Even when at operating temps the idle pressure is usually above 30, and hot cruise is above 60.

A side benefit was removing enough heat from the engine to allow me to remove the belt driven fan and run dual Taurus electric fans with out having coolant temp issues while towing.

 

[JoshH]

Good info. Thanks for sharing. Sounds like the external cooler is helping quite a bit. What size is it, and how did you plumb it in? Once I get my truck back together I'll post what I find about oil temps after the stock cooler both with and without an external filter.

 

[Turbotug]

It's one of KB's TD-EOCs. It's big, close to 26x8x3. Holds about 2 quarts.

 

[Gasuout]

Mine also failed when I was being easier than ever on it.

To me this is a key statement . Mine also failed at a time with a less than normal beating . About 1700 for a brief time , lifted and got back at it and boom . I was in the dunes doing a friggen brody and she let loose . Oil wasnt that hot either , it was early morning and air temps were cold out ... didnt make sense to me .

Shows that fatigue and heat cycling and randomness is also key here . Then there is always the possability of sticking a injector open on many motors out there too . With the hole in piston it is hard to determine if it is from blow torch injector or from crack and then blow through . Saw a low HP motor that stuck an injector and it looked very similar to mine .

I will never know and changed out that injector as a precaution .

My piston other than the crack and hole ... looked brand new . motor only had 12k on it . Could have been flawed piston out of the bunch . There are alot of variables here and no exact to figuring this out . The old term chit happens is in the mix here also .

I really expected to see some erosion around lip area from 2000*+ temps .

But no , piston and cylinder walls looked good . Just a .080 gouge in cylinder wall from oil ring being pushed out as compression skated down wrist pin through hole . Again I used 7 of my old pistons delipped in new motor .

My biggest concern with delipping piston was ... is it making piston weaker removing material there . Time will tell .

Again I went with my gut and delipped . Already knew that I could break it with the lip and trying something new was needed .

Been banging on it hard and been to Glamis 2 different times for a week each time doing the same old torture . Motor is holding together delipped . Been really beating it on the street alot .

I will have to admit though , I have been turning out early on the hills in the dunes and keeping the egts for long periods in check more . I was turning out when I saw is creeping past 1800* .

My ego didnt like not making it up the hill , but hey , not in any hurry to be down again .

In the past to tell you how hot I was getting it . I set the injector/glow plug harness on fire from heat transfer of manifolds .

Thats getting it hot .

Suprised this hasnt happend to any of you . Maybe its because I have no wind on the motor climbing hills in the dunes .

 

[Gasuout]

I installed my guage before I had the cooler. I would see average temps of 220+ just cruising around town. Put a small load behind it (or a bit of racing) and it would easily be 250+. When I decided to install the HTT I wanted some safety, being that it's only cooling is from oil, so I got the oil cooler too. Now my average around town temps are usually under 200, and even with my 37' toyhauler in tow I have to really work it to reach 240. Normal towing temps are 220ish with ambient temp in the 70s..

One thing that the cooler oil helped is the psi. Even when at operating temps the idle pressure is usually above 30, and hot cruise is above 60.

A side benefit was removing enough heat from the engine to allow me to remove the belt driven fan and run dual Taurus electric fans with out having coolant temp issues while towing.

I definately think better oil cooling is needed with us relying on oil to cool piston . I would like to add a cooler on mine for sure . I would agree that this is something all high HP trucks should invest in . It is the key to keeping many motors that see severe duty alive like in endurance boat racing and many other application . Cool oil is always a good thing .

Cant go wrong with better cooling of oil .

 

[TrentNell]

i think a oil cooler is def in my future mod list , come on johnny when are ya going to get some twins under the hood of that beast if anyone in the world ever needed them it would be you . great info guys havent really proved much but has been a ton of great info , the truth is we will never prove one thing or the other because for every truck that has broke there have been 5 others doing the same thing and lasted just fine . information is all we can hope for so when the time comes to build a motor you can look at the statistics and see what your odds are . egt's will always play a role in temperature of every engine component oil included so i think its safe to say that it should be along with oil temps the best ways to improve your odds . cylinder pressure also but stll havent found some other guys to split the cost of one of fingers systems yet .

 

[duratothemax]

we need better piston cooling, and figure out ways to stop rapid piston cooling after we beat on it. My first LLY failed that way too. Beating on it, then being easy on it, then I got into it and pop.

Whenever im on the highway beating on it, when I come to the exit where I have to get off the highway, I always make sure im in tow/haul, and as I come off the exit ramp I throw it in "3" and then 2...keeps the oil pressure up, keeps the revs up (better cooling), and really helps everything cool down before I come down to the stop light at the bottom where oil pressure drops way low and everything starts to heat soak.

 

[TrentNell]

just a weird thought but how many have actually broke something at the strip? Everthing i have broke has been pissing around on the street to tell you the truth because of that luck i dont beat on it much outside of the track unless i am testing a tune or something .

on edit to add to that thought think about how many people have ran fast at the track that have survived under big power and stock motors , and bet they have not beat on them much on the street .

 

[Gasuout]

Tommy broke his at the track . I dont think it matters though .

It is just that random .

Sharing info is good . We will all see different things . I think we found a area of cylinder pressure that with the right circumcstances and stars aligning we crack pistons .

Delipping is being tried now to stock pistons and time will tell if it helps .

I would think like alot of us think that oil cooling could be very beneficial though .

I had my thought on another thing also with my piston crack . It was early morning cool air and a warmed up motor but not hot oil .

Is it possible that the greater changes in temperature from piston to air and oil could have played a bigger role in piston cracking ramming it to 1800* . A more extreme difference in temp cycle for piston . Causing the temp cycle to go up and down more and quicker in temp difference . Would that fatigue the piston more .

Did that make sense ? Thought about this a few times . So would cooling intake charge more make this difference greater .... and cycle more or be bad .

great now Im even losing myself on this thought

 

[TrentNell]

Tommy broke his at the track . I dont think it matters though .

It is just that random .

Sharing info is good . We will all see different things . I think we found a area of cylinder pressure that with the right circumcstances and stars aligning we crack pistons .

Delipping is being tried now to stock pistons and time will tell if it helps .

I would think like alot of us think that oil cooling could be very beneficial though .

I had my thought on another thing also with my piston crack . It was early morning cool air and a warmed up motor but not hot oil .

Is it possible that the greater changes in temperature from piston to air and oil could have played a bigger role in piston cracking ramming it to 1800* . A more extreme difference in temp cycle for piston . Causing the temp cycle to go up and down more and quicker in temp difference . Would that fatigue the piston more .

Did that make sense ? Thought about this a few times . So would cooling intake charge more make this difference greater .... and cycle more or be bad .
great now Im even losing myself on this thought

i would have to say no because with the right amount of air the piston or oil would have never got that hot to begin with , remember rich is hot and lean is cool right now your are bring a 1000 deg egt change to the combustion chamber in a few sec were as with twins i dont see but a 300-400 deg change between crusing and a wide open run .

 

[Gasuout]

Agreed ... again there are those damn high egt's playing a huge role in temp up and down .

so keeping them down to begin with is again the answer .

Yes , I would give a left nut for a twin set up on mine

 

[TrentNell]

Agreed ... again there are those damn high egt's playing a huge role in temp up and down .

so keeping them down to begin with is again the answer .

Yes , I would give a left nut for a twin set up on mine

seems we have came full circle back to the arguement of the first post :rofl:
you'll get some twins on it eventually i thinks its your only choice, better go buy a welder but seriously i cant say twins are the answer to this but does argue a pretty strong cause .

 

[05smoker]

Any fears of the oil pump not being able to keep up the pressure if an external cooler is put on?

 

[TrentNell]

Any fears of the oil pump not being able to keep up the pressure if an external cooler is put on?

KB has done some testing maybe he will chime in and i would think the oil would be slightly thicker with lower temps wich should help keep te pressure up as well . what have you seen on your truck turbotug ?

 

[Turbotug]

I had my thought on another thing also with my piston crack . It was early morning cool air and a warmed up motor but not hot oil .

One thing I noticed with the oil temp guage is that oil and coolant temps ran pretty much parallel while the truck was warming up (before cooler install). Once they got around the 200 mark coolant would level off and oil would continue on upward..

Any fears of the oil pump not being able to keep up the pressure if an external cooler is put on?

KB has done some testing maybe he will chime in and i would think the oil would be slightly thicker with lower temps wich should help keep te pressure up as well . what have you seen on your truck turbotug ?

KB did a bunch of flow testing, on the truck, early on to make sure there was minimal pressure lost across the cooler's core.

I have had mine installed for around 30k miles with out issue, running the HTT and some pretty big tunes the whole time. I outlined my oil pressures earlier in this thread, definitely better.

 

[JoshH]

Just to clarify my position on my piston failure, I do not think the hot oil is what "caused" my piston to fail (my oil was also not excessively hot at the time my engine failed. I had just filled up with diesel, and had driven maybe half a mile before it let go), but I do think it is the reason it failed. I'm sure that makes no sense, but let me see if I can clarify. I'm sure some of you read about the problems Jeremy (05LLY2500HD) had with his engine over on DP. One of his problems was the aluminum in his heads was soft. The threads were pulling out of his rocker shaft bolt holes, and the nuts and washers from his head studs were pressing into the surface. It was speculated that the reason this happened is because the heads were exposed to too much heat for too long during the cleaning process of the machine work, or something like that. I believe that over time, especially when towing up a grade, the oil will get to a point that it cannot sufficiently cool the pistons, and the aluminum in the pistons is put into a state similar to what happened to Jeremy's heads. Now that the material is soft, it's power holding capabilities is diminished, and as soon as the cylinder pressure reaches more than the material can hold, it blows out. I believe that is what happened to mine, as mine blew the first time I really stomped on it after it saw the extended periods of high oil temps.

As for Johnny's engine failing at low throttle/RPM levels, some of you probably remember hearing how several rod failures happened under about the same type of situations. Maybe Fingers can verify, but it was speculated that cylinder pressure can be very high at low RPM and throttle levels because of the fuel all being sprayed in before TDC.

I can't say for sure that I'm correct in my assumptions, but I don't think it is a big coincidence that my piston failed the day after the towing trip. I have my failed piston and a good piston that was in the motor at the same time. I have considered trying to get it sent to a lab to have the material analyzed to see if it's properties are what they should be. I have another set of LBZ pistons that were not in the engine when the piston failed, so I might try to have the material from the failed piston compared to both pistons (one that WAS in the motor with the failed piston and one that was NOT in the motor with the failed piston).