[jdmerk]

assuming everything is stock on my 76 400 block how many cc's do i have to get my heads down to, to end up with a 9.5cr?

[screamingchief]

There are quite a few variables that determine just how "stock" were talking here...

But we'll go with a stock bore & stroke,with the pistons about .020" down in the hole (a pretty standard amount),with the usual valve reliefs (appx. -6cc's),and using a "standard" compressed thickness head gasket (.040").

I come up with a 77 cc chamber to get the 9.5:1 your looking to achieve.

Some of the later model engines used pistons with a large "bevel" in them too,so if these are being used that will affect the final numbers as well.

You can employ a slightly larger chamber if you get the pistons closer to "zero" deck height by any of the possible methods of doing so,or use the closest bore size/thin (.027") cometic head gaskets to reduce the "gasket volume" somewhat.

Here are a couple links to some good online calculators for playing around with the numbers on something like this:
http://www.rosspistons.com/calculator.php
http://kb-silvolite.com/calc.php?action=comp

[jdmerk]

so with 88cc heads i would be at 8.65:1, are there headgaskets out there that are thinner than .040? maybe .020...that would put me at 8.98, or is that being optimistic?

[screamingchief]

Best bet would be the .027" c/t 4.160" bore cometic headgasket as I mentioned before,the thinner compressed thickness along with the smaller bore size (4.160" vs. 4.300" for a "std.") should yeild just a bit more squeeze,also will help the chamber dynamics some by moving the piston closer to the head for better "squish".

They are'nt "cheap",but nothing good rarely ever is.

[jdmerk]

i was looking through summit online and saw some SCE copper gaskets that are .021 compressed with a 4.250 bore, is there any downside to these? they are $88/set