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#1
02-22-2004, 03:05 PM
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I'm trying to find out how the compression ratio of an engine is calculated. I have a 400 motor that is bored .040 over and I am using the Jim Butler Eagle stroker crank (4.250 x 3") with Ross pistons. The block is Zero decked and I have ordered the KRE 85cc heads. I believe The Felpro head gasket is .039 thick. I'm using the Comp Cam XR288HR cam and I want to make sure the motor won't ping on 93 octane gas.
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#2
02-22-2004, 03:05 PM
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I'm trying to find out how the compression ratio of an engine is calculated. I have a 400 motor that is bored .040 over and I am using the Jim Butler Eagle stroker crank (4.250 x 3") with Ross pistons. The block is Zero decked and I have ordered the KRE 85cc heads. I believe The Felpro head gasket is .039 thick. I'm using the Comp Cam XR288HR cam and I want to make sure the motor won't ping on 93 octane gas.
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#3
02-22-2004, 03:25 PM
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Compression calculator, courtesy of SD Performance.
 ------------------------------ My wife says I never listen to her, at least that's what I think she said.
__________________
1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
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#4
02-22-2004, 03:30 PM
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The stock bore of a 400 is 4.12, stock stroke is 3.75, you are wsing a 4.25 stroker, you will have a 462.31 cubic inch motor with a 10.60 cr. a bit much for pump gass shoot for a cr of 9.5
Its ok to giggle and snicker, Dont laugh and point
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Its ok to giggle and snicker, Dont laugh and point |
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#5
02-22-2004, 04:31 PM
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Don't forget, aluminum heads are good for an extra 1:1 cr due to the cooling nature of aluminum. My combo works out to 10.5:1 cr with the 87cc eheads and with the fuel injection runs 87 octane without pinging. But, it does run much stronger with the 97.
 TigerEFI.com (Classic Pontiac Fuel Injection) Classic Pontiac EFI Forum Jack@TigerEFI.com 68 GTO, 455 JBP EFI, 6 Speed Dual Overdrive Motto: Build it for NASA and drive it like you stole it!
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 TigerEFI.com (Classic Pontiac Fuel Injection) 2004 GTO Company car, 1994 TA 25th Anv, 1971 Grand Safari Wagon, 1968 GTO EFI, 1968 GTO Stock, 1968 GTO Convertible in desperate need of restoration. |
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