Great info.
Quote:
Originally Posted by hgerhardt
My 428 with Ross flat tops and zero-decked block and 72cc E-heads is 11.4:1 and is happy with 91 octane. Cam is 248/254 @.050 and 114 LSA.
So much of this is dependent on cam timing. It's the dynamic CR that's important, not static. Dynamic CR is determined from when the intake closes on the compression stroke. The later the intake closes, the less dyn CR you'll have.
An example: this engine with the same cam originally had 87cc E-heads (9.7:1-ish) and I accidentally figured out that it ran better on 87 octane than 91. With the 72cc heads, throttle response is sharper, and I picked up around 1/2 sec in 1/4 mile. Much happier motor!
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Can you post up details on the 248/254 cam your running please sir? Working on similar combo.
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1971 Base Firebird..505ci IA 2A Round port E-heads by Butler 348 cfm.. Comp street SR 266/ [email protected] Victor intake/Quick Fuel Q950. 1 7/8" Dougs headers..3" mandrel bent exhaust with Hooker Max Flow mufflers, T-350 well built with 10" 4000 stall nitrous Continental converter..3.73 posi . Caltracs and 10" slicks. Belt driven water pump, alternator, Pwr steering and brakes,Flex fan. 11:1compression, straight 93 octane pump fuel. 10.35 @ 129.88 with 1.45 60ft N/A at 3700lbs race weight.
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