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#1 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Vacuum value form bone-stock 396/402?
My engine builder used a slightly more aggressive cam.
Factory 1970 is 196/196 duration, .398 .398 lift Factory 1971 is 192/203 duration, .398 .430 (biased towards exhaust I guess) My cam is 214/218 and .476/.496, with 66 degrees over overlap, intake centerline of 110 and exhaust centerline of 120. A bit more than stock, but still what I'd consider a fairly mild cam (I hope). While tuning the engine I can't get more than 14-15 inHg of vacuum. That's plenty for power brakes, but I'm wondering how it compares to a factory original truck. Anyone have an unmolested, original-cam, original-everything 396 or 402 that they can tell me their idle speed and vacuum for? If the factory setup makes 16-17, I'm fine. If it's making >20, I need to rethink this cam depending on how it drives.
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#2 |
Registered User
Join Date: Oct 2008
Location: Marianna Arkansas
Posts: 7,270
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Re: Vacuum value form bone-stock 396/402?
Dave your cam is by no means a large cam for a big block. That sucks
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