I called to order my Cometic head gaskets today. I have a choice between .036" and .040". The block is "zero decked" for the 3.48" stroke/6" H-beam rod/Ross flat-top rotating assembly. The stock casting LT1 heads have been "surfaced".
Yes, it's gonna run on race fuel. Compression should be around 12:1

Typical SBC build procedure calls for .035" piston to head clearance, right? If that's the case, I should be OK with the .036" head gasket, correct?

BTW, this is going to be a nitrous motor that will see a 200 shot.

Thanks,
Frank

 

have you assembled the rotating assembly in the block and accurately measured to be sure its actually at .000 deck yet? if not, i would put it together and find out for sure what your true deck height is before making that decision on the gasekts.

 

For a mild application like that I don't think you need to deal with the potential hassles of Cometics. Also if you want 12:1, what gasket volume did you use to arive at that target with the rest of the assembly?

 

Personally I would run the wider one, .035 is the tighter end of the recommended quench spectrum, especially running nitrous. You could probably do it no problem, but if you keep it cool, especially with flattops, you shouldnt have any detonation troubles with closer to .040.

 

I fail to understand what running nitrous has to do with quench. I consider .035" closer to ideal than .040". FYI, there is no problem with .030" quench. .025" with steel rods, on a 6500+ rpm engine MAY cause the pistons to kiss the heads.

 

I agree, the quench part of the smaller one would be better, but I was just referring to the "shock" when the nitrous is used "may" cause the piston to extend further from the crank and get closer to the head. Probably not, but unless searching for every available 1HP its not worth it in my mind.

 

Under power the piston is pushed away from the head all that matters is the materials and revs. As for nitrous having an effect I would say keep quench tight but safe to help reduce the possibility of detonation. An engine will run longer with no oil than it will heavily detonating.

 

This engine will be ran on a mix of 93 octane/108 octane on the street and straight 108 octane at the track or on the bottle. The nitrous system also has an MSD digital spark retard box to pull timing whenever the nitrous solenoids are activated.
I've done all this to prevent detonation with 12:1 compression.

Frank