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Discussion Starter · #1 · (Edited)
Hey Fellas thinking about trying to squeeze a bit more compression out of my 406 build. Current is AFR 75 cc heads, .025 deck, .020 gasket...so .045 quench. with a 63 ABDC cam (comp 12-770 mechanical roller) yields 10.18 static and 8.28 dynamic. Heads I want to switch to are AFR 65cc so with same gasket and deck height I now come up with 11.32 static and 9.18 dynamic. I know I can cut it down a bit by going thicker gasket but I don't want to give up the .045 quench since I believe that is so important regarding detonation. Here in NJ 93 octane is available...any thoughts on the 9.18 Dynamic ratio with 93 octane?
 

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You're right about the quench in that ballpark. I also just purchased a set of the AFR 195 heads with 65cc combustion chamber to go on my 383, with a .010 deck and a .036 gasket for a .046 quench. At work and can't remember the exact figures, but mine worked out around a 10.75 static and just under 9 for dynamic...I'll double check when I get home.

When I was getting ready to buy these, I called Tony Mamo @ AFR and discussed this at length with him. Very knowledgable guy as he helped design these heads, so I kinda trusted what he said.. ;) But he said I would be fine with these figures. I would put in a call to AFR and ask for Tony to discuss...hard fella to get ahold of though...be patient !
 

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sounds like your combo is right on the money now. if you step it up you might have to mix your fuel with some race gas. i have a 10.1 static and a little over 8 for a dynamic on a 383 with aluminum head. i have an 8 gallon fuel cell that i put 6 gallons of 91 in and i have to put 1 gallon of 116 in it so it doesnt diesel when i shut it off. every motor is a little different though.
 

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Discussion Starter · #5 ·
I am thinking of leaving it as is, since it runs really strong and no detonation at all...any ideas on what % HP gain would go along with a bump of compression by 1 point?
 

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The compression is more than just max hp gain...its broader torque curve, better low rpm torque, more vacuum and in some cases even better mileage. That being said something like 20hp or more is possible but more important is that power you gain in whole rpm area. I would personally run with quite a high DCR with AFR heads since their combustion chamber´s doesn´t need much of a ignition advance. I think you are leaving bunch of power "on the table" with your current combo and compression.
 
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