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400 compression

3K views 6 replies 5 participants last post by  CRUSHU F150 
#1 ·
I think from memory the compression on the 400 with flat top pistons is 9.0:1 with open chamber heads (someone correct me if i'm wrong).

What would the compression be if I installed 302 closed chamber heads on it? I'm thinking it would be too high for 98 octane but not entirely sure.
Any ideas?
 
#3 ·
Just be sure to work it out carefully because the 4" stroke can really pump up the compression,more so than a 351..
One i was involved with with 351 flat tops and 302 heads was close to 12:1...The reason being i believe is the original 400 pistons are a fair way down in the hole..
 
#4 ·
I worked out on a CR calculator with:
59cc combustion chamber volume
-6.5cc piston volume
Gasket thickness 0.040
Piston .010 below deck?? not sure with this one I guess it depends on piston height?

Works out CR of 11.86:1..........still too high.

Can I get pistons with more negative volume?

Gives me
 
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