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Author
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Topic: compression calculation
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65driver
Gearhead Posts: 216
From: Syracuse, NY
Registered: Feb 2000
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posted 03-04-2002 06:03 PM
   
If I have 9:1 compression, with a 64cc head, on a 289 thats been bored 30over, how do I calculate my compression if I switch to a 60cc head or a 58cc head?
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capri man
Gearhead Posts: 7611
From: doerun, ga.
Registered: Nov 2000
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posted 03-04-2002 08:15 PM
try this 65driver.http://www.kb-silvolite.com/calc.phtml#comp1 ------------------
mike r
racing is real
everything else is just a game.
81 capri-7.56 @88mph 1/8
1.56 60 ft.
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Ron
Gearhead Posts: 137
From: Newcastle, Wa.
Registered: Feb 2002
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posted 03-05-2002 12:39 AM
quote:
Originally posted by 65driver:
If I have 9:1 compression, with a 64cc head, on a 289 thats been bored 30over, how do I calculate my compression if I switch to a 60cc head or a 58cc head?
Work the math backwards
9 X 64 = 576 - 64 = 512
so 512 is your starting point
now lets go with the 58 cc head
512 + 58 = 570 divided by 58 = 9.83
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n2oMike
Gearhead Posts: 2831
From: Spencer, WV
Registered: Jan 2001
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posted 03-05-2002 09:52 AM
First off, you don't have 9 to 1 with a 64cc head on a flattop 289. It's around 8.4swept volume = 600.3 cc
clearance = valve notches + deck + gasket + chamber clearance = 4 + 4.2 @ 0.020" deck + 9 + 64
clearance = 81.2 cc cr = (swept + clearance)/ clearance
cr = (600.3 + 81.2)/81.2
cr = 681.5/81.2
cr = 8.4 w/60 cc head cr = (600.3 + 77.2)/77.2
cr = 8.78 w/58 cc head cr = (600.3 + 75.2)/75.2
cr = 8.98 Most people over estimate their compression ratios by not taking all the variables into account. Good Luck! ------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220
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65driver
Gearhead Posts: 216
From: Syracuse, NY
Registered: Feb 2000
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posted 03-05-2002 08:27 PM
Hey, thanks for all the info!
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