Late Closed Chamber 318 heads, what CR?

[70Hardtop]

I pulled the 318 a few weeks ago. It was a replacement engine (factory assembled 1993) but the cats date on the block is 84. No cast date on the heads. The engine is black in colour.

Anyway, it has closed chamber heads -someone told me they were called "swirl chamber" heads. Normal cast flat top pistons. Does anyone here know approximately what CR these later 318's had? I think the older 318's ('73) with the open chamber heads had about 8.5:1. '71 engines had 8.8:1 . I have heard of a 9:2 CR for these heads, is that about right, or more? thanks!

 

[1967DartGT]

The CR will all depend on what pistons you have. Given a set of pistons, the "302" closed chamber heads will give you more compression than an open chamber set becasue the closed chamber heads have a smaller chamber size, but it is impossible to tell what your CR unless you know what the piston compression distance is. I'm not sure what the CR from the factory was for the "302" heads.

 

[dodgetkboy78]

Not really true, it has nothing to do with the chamber shape, but the chamber size.

CCing them, you will come up with about 8-1, the pistons are usually a mile down the hole.

 

[70Hardtop]

Thanks for the answers. Looks like i will have to get the data and plug it into a CR calculator. I heard the Keith Black site is good.