340mopar
Sorgermotorsports
What is the approx. compression ratio change say on a '73 400 between the open chamber 906/452 type head and the closed chamber 915/516 type head?
Chuck
Chuck
Compression ratio change?
- Thread starter 340mopar
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demon seed
The Original Demon Seed
Somewhere around 1 point, eg. 9.0 for the open and 10. to 1 for the closed using the same head gasket thickness of course.
340mopar
Sorgermotorsports
Thanks.
I assume milling the closed chamber heads doesn't effect the compression ratio as much as milling the open chamber because the closed chamber doesn't reduce in volume as much... But how much does it change per .030?
I assume milling the closed chamber heads doesn't effect the compression ratio as much as milling the open chamber because the closed chamber doesn't reduce in volume as much... But how much does it change per .030?
moper
Well-Known Member
IIRC Indy uses a ".010 = 1cc" deal for their heads..My guess is with the 915s/516s that's probably closer to .008"= 1cc. A lot depends on how big they start at too. I recall it being less than 1 point going from open to the closed. Closer to .75 .
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