Ok so I finally got my hands on Desktop Dyno to do some playing around with my new engine. I need to know the thickness of the Fel-Pro replacement gaskets for a 350. I used the expensive ones with the silicone around the cylinders and water jackets. Also I know my block wasn't decked, so what is the original deckheight or Piston Down Bore that they want?? Is it different than a 350 since I'm running a longer stroke now??

 

You should be able to look up the Fel Pro by part # and get its thickness.

As for the deck height, there's no way to know other than measuring. It depends on how your pistons are made, and where within the tolerance for it your block deck height is. Stock motors with stock pistons are usually between .025" and .040" down in the bore. We can all guess all day long what you've got and maybe somebody will guess right, but you won't know who until you tear it down and measure it. That should be measured and recorded as part of a build process.

 

The standard block deck height is 9.025".
This figure does vary some from block to block.
The standard 350 piston pin height is 1.56".
Some factory pistons and many replacement pistons are not 1.56" but 1.54"...

A 1.56" piston *should* result in a piston to deck clearance of .025" a 1.54" piston will come up to .045" below the deck on a "standard" block, with standard 5.7" rods.
Remember the blocks do vary and there are other pin heights too but this is the common stuff.
There is only one sure way to know YOUR compression height.
And that is to measure your stuff.
A lot of stock 350's came from the factory with a .015" shim gasket that is real near the bore size (4.10)". Felpro 1094 is the equivelent shim gasket.
The common felpro composite replacement gasket is a larger bore size (4.166) and .038" to .041" thick.
Al this needs to be taken into account when buying pistons and gaskets and machining blocks and heads.

This should give you some numbers to play with.

 

Thanks, those numbers should be good enough for what I want to see.