Hey guys
im looking for some help. I had a motor built last year for my 93 m6 camaro. Ill try to keep this as short as I can. Quick rundown on the car.
93 z28 camaro,
rear mount turbo set up (with front mount intercooler, about 8-9 psi)
tuned on pump gas 93
motor is a stroked 377, compression about 10.3-1
CNC ported stock heads and intake
No egr, or emissions to worry about
2 colder heat range plugs
ECM converted over to ob2 24x with cam sensor and 24 reluctor wheel, 8 coil set up just like GM LS1
has your pistons with coated skirts and ceramic coated tops (part # on piston is 102521)
rings are Total seal for boost, steel top, napier 2nd
car was dyno tuned for afr at 11.1-11.3

Problem I have is from the second I started the motor in the car it had more blow by than it should have (ive had a lot of other motors rebuilt by same builder). Ran a few heat cycles through it and changed oil (Rotella T non synthetic 10-30, 15/40 was put in b4 any high rpm or dyno time). Let car warm up and put a few miles on the car. Another thing I noticed was blue smoke on deceleration (under vacuum). I called engine builder and he wants sure. Said to put some more miles on motor to see if rings seat better.
After that, loaded up on trailer and took to dyno and got drivability and WOT tuning finished. Put a few thousand miles on the car and oil under vacuum never got better. I then replaced valve seals and intake gaskets twice to make sure it wasn’t that. No change at all. I also removed turbo from the intake and no change (no oil coming from turbo and intake pipes where clean).
Right at the end of last summer I was out racing a guy and did 4 pulls with him. 40-140 mph. Air fuel always looked good and have NEVER heard any knock nor seen any on the dyno with laptop. After the 4th pull I notice something wasn’t right and now it smoked under acceleration (blue). I have now removed the motor a tore it down to find about 5 bad pistons. One is melted/broken and, the other 4 are pitted bad (detonation) and the top ¼” of piston is starting to lift up. The rings have micro welding on them also. The pitting is in the same spots on all the pistons, on the outs side of the intake valve relief. Do you have any idea what’s going on here? Again AFR was always good and never “heard” any knock.

 

Looks like high intake temps & too much timing, pre-detonation.

 

yea cant disagree there.. it is what it looks like. I’ve gotten a few different reviews from 2 motor shops and the diamond piston tech... first shop says the burn pattern looks bad on top of the piston (not spreading out the fuel even) and making hot/lean spots. other shop said from the oil it was burning on deceleration it was making have hot spots or something. and diamond says too much compression and to rich AFR.....

 

End result is detonation. When oil gets in the chamber, it kills the fuel and makes it detonate (kind of like running lower octane quality fuel). Now, were the pistons burnt up and then oil got in the chamber, or was oil getting in the chamber and causing it to detonate, which caused the piston damage? That's what you need to figure out.

 

very good point. i know it was getting oil on decel... but is that enough to make fuel bad..

 

Quite possibly. Any oil in the chamber kills the fuel. If it was oiling on decel, it was oiling all of the time.

 

If the seals were good then it would be the rings or cyllender wall problems that caused oil to get in there + if you did not have a breeather on your valve covers you would have forced oil into the chambers by blowby,seen that many times with resaults like that

Mike the rings radial and compare it to the pistons and what the manufacturer says and what hone job to use with them

Check cyllender roundness

 

First thing that popped in my head was rings upside down or improper staggering. Not that I've seen those things cause this type of failure, just seems like they might could.

 

Since oils flash point is significantly higher than gasoline how would it cause detonation? Only way I see that being the case is if the oil was so hot that it was detonating the incoming fuel, but that would be a stretch.

 

Flash points have nothing to do with the combustion process. Nothing is being "flashed" in a combustion chamber, it's being ignited. If you mix oil with fuel it dilutes the fuel concentration.

 

The temperature at which a chemical will vaporize and give way to ignition has nothing to do with the process of combustion?

 

If you're getting the mixture hot enough to get to it's flash point, that's called detonation.

 

No, but I know what your getting at.

I do believe the OP's issue is detonation, but not pre-ignition and I also believe it has something to do with the oil in the cylinders. finding the source of the oil I believe will be the fix.

 

I have never had good luck with Total Seal rings, many others have so it could just be me. I used them in 2 engines and had blow-by issues, almost like they never fully seated. A switch to other rings solved the problem, used Hellfire in one and Hastings in the other. Now, with forged pistons, I use the ones that come with the pistons(usually JE or CP) and have had really good results. I have also heard of blocks flexing and causing the bores to go out of round under boost. Good luck

 

thanks guys for all the info so far!!!! love this forum!
working with CP right now.

 

I use total seal in everything. Rings are usually seated before the engine is even fired for the first time. Can't have a real rough hone job.

 

Like I said, maybe it's just me. I know people who swear by Total Seal rings, they just never worked for me, could be the machine shop's hone or it could be bad luck. Never had issues with any other premium rings, just them.