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#1
01-26-2000, 02:04 AM
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Anyone with a high,...er explaination
I was wondering, if you have a hypothetical engine (400,455)10.1 compression,ported heads, RPM intake Ram Air IV cam,headers X-over 21/2 exhaust. the whole shebang, and lets say it runs 12.50 @112MPH at "Sea Level".If you race @ 4000 ft above "SL" your times would be 13.00(??) MPH 109(??) just a guess. To compensate for the change in altitude you would need to lean your fuel with smaller jets(a couple of sizes), but wouldn't you also need to raise your compression? and or advance your timing, by how much would you need to raise the compression? Is there a rule of thumb 1 point for every 4000ft or something like that or is it all trial and error? I have heard that having an 8.1 compression engine is like having between 61/2.1 or 7.1 at roughly 4000ft above SL.Any truth to this Thanks for your help
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Jim Moshier 1971 Grand Prix 462ci SD Performance 6x heads 1962 Catalina 389 1968 Firebird 400-455 I haven't decided "If we ever forget that we're one nation under GOD, then we will be a nation gone under." - Ronald Reagan |
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#2
01-26-2000, 02:04 AM
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Anyone with a high,...er explaination
I was wondering, if you have a hypothetical engine (400,455)10.1 compression,ported heads, RPM intake Ram Air IV cam,headers X-over 21/2 exhaust. the whole shebang, and lets say it runs 12.50 @112MPH at "Sea Level".If you race @ 4000 ft above "SL" your times would be 13.00(??) MPH 109(??) just a guess. To compensate for the change in altitude you would need to lean your fuel with smaller jets(a couple of sizes), but wouldn't you also need to raise your compression? and or advance your timing, by how much would you need to raise the compression? Is there a rule of thumb 1 point for every 4000ft or something like that or is it all trial and error? I have heard that having an 8.1 compression engine is like having between 61/2.1 or 7.1 at roughly 4000ft above SL.Any truth to this Thanks for your help
__________________
Jim Moshier 1971 Grand Prix 462ci SD Performance 6x heads 1962 Catalina 389 1968 Firebird 400-455 I haven't decided "If we ever forget that we're one nation under GOD, then we will be a nation gone under." - Ronald Reagan |
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