Well I took my drivers side head off as the result of the leakdown told me # 3 cyl was screwed. To my suprise when I took off the head I found damage to pistons 5 and 7, My rings may be shot on my # 3 piston but I could not see any visible damage to it. Here is all the pics that are crappy quality but you can see whats going on.


It looks as though the edge of my 5 and 7 pistons was melted away at the ends. The cylinder walls are still smooth and I can still see the cross hatches somewhat so my block looks to be salvageable. Also look at the cylinder head pictures. The arrows are pointing to the material that came off of the piston and fused to the cylinder head. What do you guys think caused this ? Perhaps I was detonating and running to lean on those cylinders? I included a pick of what the spark plugs looked like out of those cylinders as well.

Looks like I will be doing the stroker motor cause my motor looks like

 

The plug does show detonation with the little pits. Not sure on the pistons though. Sorry.

 

Detonation, pure and simple. I had customer's car do the exact same thing and I had a motor I built with stock pistons do it as well, all from detonation. In my case, it was too much compression, timing, and the Louisiana summer heat that took the toll on mine. The stock pistons are pretty strong, but they do not like to be detonated at all (very brittle).

I attached some pics of what happened to my stock pistons.


When you pull the motor down, this is what you are likely to see

 

i see you have ls1edit but who did you tune and what wideband did they use?

 

It was done up North by JPR when I went to up there to get the head/cam package. It was at JD's dyno. MY a/f was right at 13.1 during the runs and my timing was set to 28 degrees. Damn Jason those pistons were messed up, I'm anxious to see what mine look like after the tear down.

 

sorry to see that man.

That shot of the plug with teh specs of (formerly) molten metal reminds me of how the Eclipse's plugs would look after crossing the traps at 1700*, but they were never even remotely that bad...oy.

Good luck getting her back together with a new tune.

-Jake

 

Thanks for the post. Very interesting , great pics. No nitrous???

Do cyl #5 and #7 commonly run leaner on ls1s? Thanks.
joel

 

Bummer. Are you running the stock injectors? Fuel filter dirty? Done a pressure check on the fuel system? I would before I ran it again, those pictures look like the engine detonated. So I would suspect something is wrong with the fuel system. Maybe add the insurance of an external pump and regulator.

 

I have the fms 30lb's but they are the ones from summit which are not flow balanced. They are like -5 to + 5% difference. Maybe that is what did it? Other than the injectors the fuel system is stock. I will get the fuel system checked for sure. One thing that is kinda funny is that I found a wire harness the other day by the fuel tank and one of the plugs was just dangling by my rear end. There is like four different plugs on the wire cluster and only one of them was dangling. I wonder if this has something to do with a connection to the fuel pump ? I'll get a pic later of the wire cluster I am talking about. And yes this is with no nitrous or power adder whatsover.

 

I was under the impression HEAD/CAM (only) cars were damn near bullit proof!

 

#5 and #7 are always the problem children. I know from from experience in my car. I cracked a piston about a year ago on #5 and #7 had the ring lands damaged. All the others were normal. This was from a fuel pump failure on the dyno.

 

Hmm thats odd I wonder what makes these pistons weaker than the others? Weird

 

The pistons are burnt off on the exhaust side due to excessive exhaust gas temps! Running too lean with octane too low. Each cylinder will act differently. You could have one piston with a hole in the center and the next one could be fine! They round off like that from the heat flowing past the piston into the header! My guess would be that your exhaust gas temps were higher than 1400 deg.!! Richen up a little, and try to find better gas! BTW did you know your a/f ratio? I would like to know. Good luck Andy.

 

A/f was 13.1 which was confirmed on multiple dyno's. I will have to richen it up a bit to be safe the next time around. I had been using 93 octane Amoco and I had recently switched over to chevron and was using chevron when the failure occurred. I was under the impression that chevron was one of the better gases. I'm also thinking next time around I'll get a set of flow matched injectors to be sure they are all spraying the same.

 

i didn't see you answered my question before , whose wideband was used and when was it last checked

 

Stick with shell, amoco, mobil. All other gas sucks! You also might want to take a LITTLE timing out. I would bet the farm you problem came from the gas! Gas is SO bad. I try to find a good station and stick with it. I do a water test and a alcohol test on the station I use local. It happens to be a shell station. You never know what your getting. Good luck with the rebuild. I happen to have a brand new set of coated diamond pistons and rings for sale? Andy

 

Mike, do you know what your compression ratio was?

 

I used a wideband up in New Jersey at Jd's and one down here at a place called Secret Services. Believe it or not I was just on the dyno like a week before the failure. Funny thing though on the first run I was down 20 hp and 20 tq on the 2nd and third runs I was back up to normal. On the first run alot of black smoke blew out the tailpipes. 2nd and 3rd runs showed no sign of smoke.


Here are a couple of my dynos.

First dyno was done about 2 months ago. 2nd dyno was the run that was a week before the failure, So you can see my a/f.

 

My heads were the 5.7 ltr and they were milled .030, I do not know the exact CC size but with the valve reliefs I would guess my cr was anywhere from 10.5 to 1 to 10.8 to 1.

Last LS1 what kind of pistons are they the flat top with the -2cc reliefs with 3.905 bore?
PM me with the exact specs and price

 

Was the pcv suckin oil into the intake? Oil contamination will lower the octane rating of fuel. Maybe the 5 and 7 cylinders get most of the oil from a leaky pcv. Just tossin in an idea for a possible cause.