Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - hi or low compression??
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Old 10-13-2012, 01:37 AM
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Quote:
Originally Posted by OMARS67 View Post
do i guess right to think a 119cc head would raise the compression on my 454 BBC. currently i run 148 heads with 122cc but i have pretty tall dome piston. given i use the same gasket for both heads.
First, the advertised volumes are almost never right, the real volume of an unmolested head tends to be a bit more.

That said, the chambers have to be CC'd in order to know exactly what you have. If the heads have been milled, they can be radically different (smaller) than advertised and this can affect the piston to valve clearance. More things to check here. Changing valve sizes, unshrouding or polishing the chamber, valve jobs, etc. can all change the chamber volume.

You are right that a 119cc head will raise the CR over a 122 cc head. But you're only looking at about a 0.2:1 change- so if you're doing this only for the rise in CR, don't bother.
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