[tomthecomic]

I have a topend kit that I had on a 350 and just got a new short block. It recommends a felpro with a .039 and I am also looking at a .041. I know this is not much. Will the .041 lower my compresion. The new block has a 10.4 I would like to lower it a bit. Will the .041 gasket cause any problems? Also will my push rods need to be longer.

[chas350]

What shape are the piston tops?
How far in the hole are the pistons?
A good quench (flat areas between piston and head) of .040 is desirable and sometimes lets you run a little more timing, reduces pre ignition, helps equalize the cylinder performace.

You will need these answers for the pros here (not me) to help you.

Good Luck

chas

[tomthecomic]

the pistons are round. no no they are flat with 4 valve forged. I dont know how far in the hole I do know it is not much. Wish I was more help. I am picking it up today and will ask

[chas350]

Tom, if you are getting it from an engine shop, ask them to put a dial indicator on a few cylinders and check how far down from the deck they are, then write all of them down. If this is just a private purchase, stop by a local machine shop and ask them to measure it for you. Make sure they measure from the side of piston that is parallel to the crank so any piston rock is eliminated from the equation.

chas

[jimfulco]

The compression ratio difference between those two gaskets on a 350 would be well under a tenth of a point.

[tomthecomic]

I guess I will go with the .039. The motor guy did not know much. Makes me feel good about my purchase

[ScoTFrenzel]

Originally Posted by tomthecomic

I have a topend kit that I had on a 350 and just got a new short block. It recommends a felpro with a .039 and I am also looking at a .041. I know this is not much. Will the .041 lower my compresion. The new block has a 10.4 I would like to lower it a bit. Will the .041 gasket cause any problems? Also will my push rods need to be longer.

Round pistons. LOL

Copper gaskets are available in several different thicknesses. .060 will help your compression problem. You might find something more suitable for your desired compression. Thicker head gaskets also necessitate thicker intake gaskets and longer pushrods.
You will lose squish/quench, but that is the price for lowered compression by thicker gaskets.
I would consider Singh grooves.