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#1
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vacuum rule
Once again, the local track has screwed us. They are going to combine, street stock and pro stock. My chessman chassy is outdated. Can't run my car in either class. Thinking I will race in OKC, (factory stock). I must pass a 16 inch vacuum rule. Was courious to what cam to run 318, 9-1 flat tops, stock intake, with headers, any suggestion's would be helpful and appricated. Also, have a A body duster. Pro built that has ball joint's, in place of front strut rod bushings, these have gave me hell all year. Just wondering, if they are for front bump steer and if they are old kit car technology. Once again, I look stupid, but I'm a old drag racer, starting to race dirt. Just wanted to know. Thanks, Scott.
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#2
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If all they do is check your engine to see if it can pull 16" of vacuum then all they are checking is camshaft overlap. Compression, camshaft lift, to a degree camshaft duration, cubic inches and cylinder head modification do not affect vacuum. Can you run a 360? I would if permitted.
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#3
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About the only other thing that affects vacuum is timing. I think you could get the 16 inches with a bunch of advance, then set it correctly when you race. If they check you right after the race, then you may have to go to plan b. I will try to check on the computer programs what the estimated idle vacuum is for different cam combinations.
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#4
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thank you 340 I knew if any one could help you could. they always take us to the barn right after the A.The rules say it must pull 16 lbs. at 1000 rpm.they can also puff test too, static compression canot be over 150 psi. single line holleys or stock carb only.the motor I have in it now is out of my wife,s pure stock 9-1 pistons and stock heads (318) I have a 360 and a set of J heads but they have been milled 20 thosands. I,m not sure if I will pass the puff test with 10-1 kb.I ran that motor in street stock this year but got it hot and blew a head gasket.next year steet stock will be able too run weight jacks and 3 links. I not sure this old chassy will keep up. thats why I,m thinking about moving down a class.Now I wish I would have built an imca but i,m just starting out and thought it to be to much for a first car
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#5
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What about using Rhoads lifters? That should affect your overlap at lower RPM's while still allowing you a decent cam at higher RPM's.
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