1991 RS 305

Heads are back from the machine shop. 56cc is what they have been milled to. Does anyone know the dish in CC's that the stack piston is on the LO3? How about how far the piston sits in the hole at TDC? I have been looking for this info all over the net/ manuals and cannot find it. Anyone know the thickness of the stock gasket for sure, is it tin or composite? If anyone has this info you'll be my hero. I know I could probably run a tin (shim) gasket that is .015", but this may mess up my quence. This would probably leave me at about 10:1 compression, which would be cool, but not if the quench is messed up. I will run a thicker composite if necessary, but I want to go with at least 9.5:1 compression.

One other question... will I need new intake bolts for the vortec intake?

Any help here is appreciated, I'm in a jam until I get this squared away.

THANK YOU, Matt

Dewey316

Stock they "should" be .025" in the hole. not "should" is in quotes.

If you have the heads off, it is easy enough to check. going with a .015" stock style gaskets, puts your right at .040" quench. Most peopel shoot for .036 - .040 quench, so you are right where you should be, but on the safe side, considering you are running on older rods, i wouldn't want to push the quench threshold. This way you ensure that there will not be contact between pistons and heads.

1991 RS 305

Do I need the gaskets for the 305 or for a 350. Heads are off a 350 , but milled to 56cc, i'm putting them on a 305. I have read both ways in my searches. Also, I am leaning towards the .015" shim gasket. The block has 130K on her. Anyone think I'll have any sealing issues?

Thanks, Matt

Dewey316

I used the shim gasket with no issues at 197k. If you are worried, make sure you copper coat it. Then warm it up to temp after you are done, and then let it cool down, and retorque. You should be fine then.

IIRC I used fel-pro 1094 for mine. Do make sure you do a GOOD job of cleaning the surfaces of the head and block.