99SSragtop

A friend has a 396 motor with a blower (ATI ?) on it and it keeps popping a head gasket.To everyones suprise including ARE they go back to the drawing board.Any ideas.

<small>[ August 20, 2002, 09:27 PM: Message edited by: 99SSragtop ]</small>

AlienDroid

What's his compression ratio and how much boost?

Boosted LS1

Detonation is the usual reason unless he has really high peak cylinder pressures which would probably cause the detonation in the first place. Mike.

99SSragtop

Boost is at 7.5psi and Compression is stock at 10.5:1. The motor should be able to handle up to 11 psi safley. ANything over that I am told would need race gas to be safe.

right from the horses mouth.

30thta436

iTrader: (10)

Probably detonation. Has he dynoed on with a wide band o2 to see what his fuel ratio is. I Lifted both head gaskets at 12 psi because I was detonating. It was running 14:1 above 4k.

Boosted LS1

I reckon the boost is to high for your compression ratio allowing only short bursts of acceleration. As a rough guideline I guestimate 3psi boost is equal to 1 ratio of compression. So by my reckoning you would be on 13:1 C/r appx. I reckon that's borderline and still think you have detonation issues to check out. Have you tried water injection? Mike.

AlienDroid

How is it tuned? Are you using bigger fuel injectors? I think it should be able to handle 11 psi at that cr on a very good and concervative tune, but 11psi is a little high. I don't know how the ati blower works but I'm assumeing you're getting almost 11psi to the intake mani, whereas a turbo setup would loose some boost. Do you have an intercooler or aftercooler or whatever the supercharger guys call it?

JimmyKash

That much boost and that much compression is OK despite what people will tell you

BUT

you probably have too much timing which is causing detonation and causing those head gaskets to pop

Maybe a more conservative tune via LS1_Edit is in order