Hi Mike,
David Vizard has 2 pages devoted to calculating the compression ratio in his
books. In the first edition, it's pages 198 and199. It is more intimidating
looking than it really is, so don't be that fearful of the pages.
He covers all the nooks and crannies that you should consider on this
calculation, even the bit about shaving your deck.
If you don't have the book, I can scan the pages and send to you.
The combustion chamber size on a 948 head is normally 24.5 cc. The chamber size
on the 1098 head is 28.3 cc. So if lowering it becomes a problem, you might
consider a 1098 head instead of a custom made thick gasket. This head also has
bigger intake valve and has long been a fave head with the 948 Morris folks to
get more power cheap from a 948.
I think that all US cars were supplied with the 9.3:1 compression ratio, not the
lower 8.3:1 The engine tag should have an H on it for high compression. If you
have the tag, look at it.
FWIW.
Regards, Paul A
Mike Maclean wrote:
> This has probably been done before, but how do you figure your
> compression ratio? I know this is going to make my head explode. I was
> thinking that the problem I was having with the Judson and the
> overheating of the engine may be due to high compression. When I
> rebuilt the engine I had a cleanup cut done on the head and 10 thou
> taken off the block. While this will not raise the compression
> dramatically, who knows how many times it was done in the past to the
> block and the head? If I can figure the compression ratio, how can I
> figure how thick of a custom copper gasket will bring it back to the
> 8.3-1 ratio that it originally was?
> Mike MacLean-60 Sprite
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