How much to mill?

  • Thread starter Thread starter Anonymous
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Anonymous

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My 1955 223 blew a head gasket friday, and I've got the head off and am taking it into the machine shop Monday. I want to shave it and raise the compression ratio to the 8.8-9.3 range. The stock ratio is 7.5 according to my shop manual. my question is-how much to shave off?
I went through all the posts in the vintage section and the only ref I could find to an amount was 215flattie saying that he had shaved .060 off a '54 223 to up the CR, but he didn't say how much that raised it.
I've CC'd the combustion chambers, and they are 84cc's. I don't have any fine measuring tools, other than a dial caliper. The software that I'm using to figure CR says my CR is 7.6 and that my combustion chambers need to be 65cc's in order to make 9.4.
Any suggestions as to how to measure the amount of surfacing I'll need?
 
Otherwise you're looking at domed slugs, right? No way of gauging the gasket face thickness?
 
the gasket face thickness is .039, I'm milling 20 thousandths off (it's in the mach. shop now) as I don't want to mill too much off. I'll cc the combustion chamber after it's milled and check the ratio, but I'm not going to tear down the engine for a complete rebuild 'til it goes south completely.
 
Does milling the head alone really do anything good for compression/performance? It seems like you'd be altering the shape of the combustion chamber more than you're really increasing compression. Doesn't seem like you'd be doing anything for better quench.

Just asking

Thanks
 
Yeah, milling will alter the shape... into smaller combustion chambers. That will bring the CR up. I don't believe that 223 has much quench to harm anyhow.
 
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