Compression
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Elder User
Joined: Dec 2005
Posts: 557
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Compression
I have a 1984 Ford F250 4x4. My truck has the 351W in it right now, stock 2bbl carb and manifold. this spring'ish im doin a cam, 4 barrel carb and manifold swap. My question is to pickup a few more hp and still run 87 octane is how much can I bump the ratio up before I have to run a higher octane fuel? The only cheap way I can figure is to run a thinner head gasket to bump the ratio up a little bit. Any Ideas on more HP?
Thanks,Matt P.S. I think my ratio is 8.5:1 right now. I'll check the books when I get home.
Thanks,Matt P.S. I think my ratio is 8.5:1 right now. I'll check the books when I get home.
Posting Guru
Joined: May 2004
Posts: 2,223
Likes: 2
From: Billings Montana
Just doing those mods you mentioned won't bump up the compression ratio. If you go to a thinner head gasket, shave the cylinder heads down or the block or put in longer connecting rods, that would raise the ratio. The mods you want to do will just give it better torque and high RPM horsepower.
But generally speaking, anytime you go over 9.5-1 compression ratio, you need to up the octane to at least 89 and anything over 10.5-1 needs 92 octane.
But generally speaking, anytime you go over 9.5-1 compression ratio, you need to up the octane to at least 89 and anything over 10.5-1 needs 92 octane.
