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Thread: What size runners for sbc

  1. #1
    Senior Member MASTER BUILDER
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    What size runners for sbc

    I'm building a new sbc which will end up as with 406 or 427 cubes displacement. Naturally aspirated with carb. 2 question, how big runners on the cyclinder heads and how much carb do I need to get max performance. This is a race engine, no street.

  2. #2
    Senior Member MASTER BUILDER
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    Thats a loaded question. What are the goals? How much power, how many rpm, car its going in, ultimate et desired, what tranny, gear, converter, how heavy, cam type, head type, intake type, etc, all come into play. You could use anything from 220-300+cc, depending on the head type, 23 degree, sb2.2, 15-or 18 degree, etc etc.

    Frank

  3. #3
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    Well I have to start somewhere. The car is your garden variety 85 Camaro. 3000lbs with me in it. I have no idea what the hp will be since it's in the planning stages now. This is a bracket car. I would rather buy the heads and match the cam to the flow of the carb and heads. The track this car will normally be run at is 1/8th mile. Tranny is a turbo 350 with a 3500 stall, rear end ratio is 4.88.

  4. #4
    Senior Member RACING JUNKIE jmarksdragster's Avatar
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    I'll assume with the 3500 stall it will be a milder build, anything 200 cc to 220 would work fine, if you go with the bigger cubes up to 230 cc. Darts are really good as cast, minor bowl cleanup and a good valve job they will work very well. Keep your @ .050 duration on the intake to around 240˚ to work with your converter, a little more with the 427 is OK. Super Victor and an 850 DP or 1000HP. I ran an 8.59 in my old dragster with a 406, roller cam, 200cc Iron Darts, Super Victor, and an 800DP.
    Mark Whitener
    http://racingfuelsystems.myfunforum.org
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    Good work isn't cheap, and cheap work can't be good.

  5. #5
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    Its been awhile since I last read this, but, if its a race only deal at 3000lbs, I am assuming you are leaning towards 23 degree heads. I would max the compression, 13-14:1, which will allow 110 octane race gas thats readily available. I would use Pro-1 Platinumn or RHS 235's on that cubed deal. The cam matching to flow numbers thing is over ratted. You sorta need a "plan", as its not really about matching this to that after you get it. If you know what you would like to run for an et, its really easy. Just throwing a bunch of stuff together and its a mystery to what it will run, isn't how I do it, but I guess I have been doing this stuff for 20+ years and know what works and what doesn't.

    Also, if its a true race car, then I would run an 8 inch converter, that stalls in the 5000+ rpm range, the car will be faster with a wilder converter. Put a big cam in it, 270's+ at .050, a big carb, etc, and you should have a 9 second ride. Mid 10's would be almost hard not to run. do you have any et goals? Thats going to determine everything. otherwise, we are all guessing at what you need. If you said i want to run 11.50's because i have no cage, well, then that changes everything. if you said, I want to run as fast as possible, then, obviously that changes everything again. Then, the budget end comes into play, how much you willing to spend?

    Frank

  6. #6
    Senior Member MASTER BUILDER
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    I kinda forgot about this post. I have a lot of fun with this car and I want to make it as fast as I can. I was going to use the existing gm block, but I think that ship has sailed. What I want to do is go with a Dart block (406 or 427cu),.not a SHP block, Calles crank, Ross pistons, rods?, probably a Lunati solid roller. Intake I don't know, RHS heads. Valves, springs, carb undecided. I'll take your advice on the converter. I haven't weighed the car. It's an 85 Camaro.


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