I have a gen IV, 5.3 aluminum block converted to a tall deck with a 1/2" plate and sleeved top to bottom (ERL style). It has 4.25 stroke and 4.185 bore for 468 cid. It runs Wiseco forged pistons with 14:1 CR on E85 making over 800 shp NA. The engine has a Mast LS7 pattern intake manifold, LS7 WCCH heads and a Dominator throttle body with EFI.

After about 10 minutes running at or near max power in a race boat it had a loss of oil pressure and I shut it down. Upon disassemble I found the problem with the oil pressure which is unrelated to what I discovered in the cylinders. On 6 out of 8 cylinders I found a very hot spot at the top of the cylinders on the side nearest to the outer edge of the block. Only the front 2 cylinders were not showing this problem. The hot spot was so intense that it cracked all 6 cylinders. This is directly under the minor quench side of the combustion chamber under the spark plug.

I do not have pictures at this time as the block is at the machine shop for repairs. I have seen hot spots between cylinders on siamezed blocks before, but never at the bottom of the cylinder.

I suspect a lean condition or detonation, but I do not know what else could cause this. I don't know if E85 has different burn characteristics that might cause this. Also, the 1/2" deck plate means the cooling water is that much farther from the top and may have contributed to the hot spots due to limited cooling in that area. I find this hard to believe because this is a siameze block and the sleeves between the cylinders have even less access to the water jacket and they were not hot there. As to detonation, I have seen it before and it usually starts near the top of the piston above the intake valve, not at the bottom. Also, the pistons did not show any indication of detonation or vaporized aluminum. The spark plugs did not show a lean condition, but I may not have enough experience with E85 to read them correctly.

Has anyone seen this happen before and know what might have caused it?
MrE

 

You may be running lean if you are tuning to gasoline stoichiometric readings, which is 14.7. Stoich for E85 is only 9.765. Tune accordingly. Here is a chart.
http://www.yellowbullet.com/forum/sh...d.php?t=293680

 

Thanks for your comment, I am using Lambda to tune the AFR and I have the correct stoich in my PCM. Neither the plugs, pistons or combustion chambers show lean, but I plan to add fuel just for the additional cooling effect when I go back together.
MrE

 

Wet flow/AFR and to much timing will do that as you are close to lifting the heads/melting a piston by what you describe and that is why you spun a main bearing if im guessing right? its all related