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Thread: compression ratio and horsepower

  1. #1
    Senior Member MASTER BUILDER
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    compression ratio and horsepower

    say you have a real healthy sbc with the good heads and cam and intake etc and you eith add or subtract a point of compression. how much hp is lost or gained with each 1 point change of compression ratio. would appreciate help in understanding what a change will make on my engine thanks chevy art

  2. #2
    Senior Member MASTER BUILDER
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    It's usually 2-3% per point in compression between 9-12 but I think it drops down to 1-2 above 13:1 this is assuming your using the same cam. your obviously going to make alot more power if you use a cam that is matched to a higher cr.

    cam67152

  3. #3
    Senior Member EXPERT BUILDER
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    complicated, correct though, its like this going from 9 up a point is say worth 5 percent.going from 10 up a point might only be worth 4 percent.going from 11 up a point might be only worth 3.5 percent....get it?

  4. #4
    Junior Member APPRENTICE
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    This is a pretty good article by David Vizard that does a good job explaining what happens in "theory" with compression changes.

    http://www.popularhotrodding.com/eng...eze/index.html
    '78 Chevy Luv--383
    '68 Camaro-- 383 Twin 60-1 turbos
    '69 Chevelle--385 N2O

  5. #5
    Senior Member MASTER BUILDER
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    compression ratios

    thanks guys for the response. before i saw the chart i understood how it worked from the frist two posts and the chart gave more final figures. now i know how this works and will use it in the future chevy art

  6. Racing Junk


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