Alright guys, the trans am has been acting up lately and never running good. I keep fouling the number 8 plug. No matter what i do it will foul that plug and run bad. I recently pulled it out and it was wet. I smelt the plug and there was no fuel smell. So we decided that maybe it was an oil smell. Well i jsut tore the head off and that cylinder looks very clean when all the others are dirty. All gaskets were fine though. Heres the major thing, The damn piston ring looks broke on the very front cylinder on that side. Im not kidding, It is shattered. WTF!!!!!! How does this happen, i know it was put on proper, What could cause this?

 

So you are saying that #8 looks cleaner than the others, but #2 looks like it has a broken ring? Could it have been broken on installation?

Also, a clean cylinder is usually a sign of a head gasket leak. The water and coolant will "steam clean" the cylinder as the engine runs. I know you said the gasket looked good, but maybe a small leak or some other way coolant was getting in there.

 

Well the piston is clean on number 8 but the head and the piston are covered in oil, The head is not clean, It is very black on the number 8 cylinder and covered in oil, The piston looks cleaner than the rest but is very covered in oil. The if you move up to the number 2 cylinder, the piston ring looks shattered. It really looks like it is in a 100 peices. The motor has about 12 lbs. of boost on it and has got about 200 miles on it since rebuild. It has done fine since rebuild until a couple of days ago.

 

You neglected to mention the 12 lbs of boost. How about a little more info on your setup.

 

383 afr heads, blower cam, vortech s-trim. 42 lb. injectors, fuel system

 

Ok, so maybe not a coolant leak. What LSA is your cam? I am not an expert on such, but don't people with blowers run an higher LSA (like at least 114).

 

yeah it is a 114, just found out that the rear cylinder, number 8, also has a broke piston ring on the top. I ahvent got the motor out as i only have this one head off. BUt its not looking good at all

 

Sounds like you went lean and took out the ringlands. The 42 lb injectors seem a bit small for that motor. What kind of pistons were you using?

 

They are forged pistons, Probe's.

 

They were forged pistons.

You may need to look at an impediance converter box and a set of low impediance injectors. I'm assuming you're still running the stock PCM, BTW.

 

That boost thing was something we needed to know. What are (ops...WERE) you using for rings. Stock LT1s hate boost, and if your gonna run that much you've got to build it to take it.

 

What ring gap did you use?

 

What was your compression ratio?

 

Do you have it apart yet? Most likely the primary failure is the piston ring land, not the rings per se. OTOH, detonation can break rings as well. You are going to need to rebuild your motor and you can't really tell what went wrong until it's torn down. Many possibilities: wrond rings for the psitons, too small ring gaps, piston ring land failure or ring failure (caused by detonation), etc. I suspect detonation induced damage of some kind though. If that's the case you wil need careful setup and tuning the next time.

Sorry for your broken motor.

Rich Krause

 

To me this is a more or less clear cut case.
When running boost on an engine and you have probs with piston rings and the cylinders look fine you´ve run into detonation-period.
If your rings would have but together you´d see evident marks of this in the cylinders.
Losing especially the top rings in a scenario like yours is another dead give away.
Engine needs to come out plain and simple.
When you do so spend some time checking the slugs over as-like have been noted-the ring lands might have started moving around too.Forged slug or not.In fact more so with a forged slug then cast or hypereutectic as those will crack and shatter at a much earlier state the the forged counterpart.

When setting up for the new rings do NOT cheap out.
In boosted apps there´s a lot riding on those rings!
I for one am partial to chrome top rings in boosted apps as they primarily have a larger heat range allowance then anything else out there when you start comparing rings vs amount of money.