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Old 07-26-2012, 10:53 PM
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BigEd36 BigEd36 is offline
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Bygddy, I wasn't so much recommending the 1003 head gasket, as stating that it would be a way of opening up the quench to .060 as mentioned by my87Z. All of the compression ratios quoted have been assuming your block has not been decked since you mentioned using .015 thick head gaskets, or at least the ones I gave were. The .015 gaskets are usually used to raise compression on a standard 9.025 deck block with standard compression height (1.56") pistons that are nominally .025 "in the hole". Add the .025 piston deck height to the .015 head gasket thickness and you will have .040 for a good effective quench. This raises questions that I haven't seen addressed here. Has your block been decked? What is the piston deck height measurement? (How far the top of piston is below the block's deck). The piston deck height added to the head gasket thickness is your quench distance, which you want to be .035 - .045. Closer is better, but less then .035 the pistons could hit the heads are higher rpm. The wider it gets the less effective the quench is, decreasing compression ratio but increasing the chance of detonation. Over about .060 there is little, if any, benefit from quench (why I'm not really recommending the thicker head gaskets). If your block has already been "zero decked" (milled to put the piston tops level with the top of the block, or .000 piston deck height) you wouldn't be able to use the .015 head gaskets because your quench would be a too small .015, and it would also make your compression ratio even higher than the 11:1! Depending on whether or not your block has been decked, how much it's been decked if it has, and the compression height of the pistons used ("rebuilder" pistons are usually 1.54 compression height, .020 shorter than the standard 1.56 compression height pistons) your pistons could be anywhere from .000 deck height (level with the block) to .045", or more, "in the hole". With a deck height of .045, even with the thin .015 head gasket, your quench is still a pretty in-effective .060. Back in "the day" before I even knew what quench was I had a 355 built by a big-name machine shop. It never ran like I thought it should. Come to find out later the pistons were .057" in the hole! If I could have put that engine together and ran it with NO HEAD GASKETS I still couldn't have gotten a very effective quench! Add in the fact that I used a cam that was slightly too big for the compression ratio that I THOUGHT I had instead of what I ACTUALLY had, and it was the most disappointing engine I ever owned.

Ideally, for your setup, I would like to see you use some larger chambered heads with a piston/head gasket/block deck height combo that will give a .040 quench and lower the compression ratio to a more pump gas friendly level.

Last edited by BigEd36; 07-26-2012 at 10:58 PM.
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