chevyart

what is the ideal quench height to get when assembling a sbc for racing..is this really important for maximum efficiency?. i know it may be hard to arrive at an ideal numberwhen things are altered, such as decking the block, milling the heads, and probably changing head gasket thickness. thanks art

hotrod1994

the ideal quench height is zero but that cant be achieved so it is as low as you can get it it the distance form the top of the pistons at tdc to the top of the deck and the thickness of the gasket added together any thing up to 35-40 thousandths is ok

chevyart

thsnks mr big i thought i had read in one of the books that a real good # is around .020 if you can achieve it that low. i know zero deck heigth is optimum, but hard to get to with so many variables in the build. art

zipper06

There's a lot of variable's in your question, but as suggested "0" deck height is a good starting point. It definately depends on the piston dome and if you're runnig gas or alcohol, example- gas doesn't like more tan 13 to 1, where alcohol luv's compression, 13 to1 up to 15 to 1 or even higher if you can get it. I never buy the gaskets until i've installed the rotating assy i then set the heads on less any gaskets with a few bolts modeling clay on top of the pistons. Ideally if you can get .050/.060 clearance thru out the combustion chamber, install a few rockers to check the valve clearance, min. .080 int. and .120 exh. with a .040/.043 gasket. You have to allow for piston rock and that can sometimes be as much as .010 with .0055 bore clearance. I have run the pistons .015 out of the hole on a gas motor with .043 gaskets with 13 to 1 but i can tell you the flat side of the piston was just touching the head with an 8,000 chip, real dangerous. That was 358" engine and it ran 10.70 @ 126 in a 3150 lb 66 nova with 492 steel heads fully ported. Perfect for S/ST.

JMO

Zip.