what size Throttle body?
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From: Greeley Co
what size Throttle body?
I know this toppic has be beat to death but i can't find the answer that i'm looking for. I know a 52 mm tb is supposed to flow 790 cfm and the 58 is 1000, but how much hp can that cfm represent? I guess i just don't know what size TB would be best for my 383 set up.
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Re: what size Throttle body? (85vettelovin)
ski_dwn_it probably has some calculations for you to use, but its fairly hard to actually use all 790cfm of that flow, thats alot of air.
So realistically, you would need a pretty radical combination to actually be able to use 800cfm of air or more.
I dont know enough people's results from the HSR to be able to really say whether it does any better with stock or 52, but you wouldnt hurt anything by running a 52 on a HSR'd 383, i think.
So realistically, you would need a pretty radical combination to actually be able to use 800cfm of air or more.
I dont know enough people's results from the HSR to be able to really say whether it does any better with stock or 52, but you wouldnt hurt anything by running a 52 on a HSR'd 383, i think.
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From: lakeland fl
Re: what size Throttle body? (vader86)
also, when comparing to, say, a carb CFM, remember that a TB is dry flow, verses wet flow of a carb; so that 790 is bigger that it sounds.... 52mm is the way to go on the street- heck, Lingenfelfter used the stock TB on the 254mph Sledgehammer.
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From: Dallas Tx
Re: what size Throttle body? (johncazin)
Theoretical Airflow is RPM X CID/2 (remember, 4 stroke engine) / 1728 (CI per CF). Also reduced by Volumetric Efficiency, which in a street engine rarely exceeds 90%.
For the sake of argument, assume 7000 RPM in a 383 CID with 100% volumetric efficiency.
Result is 776 CFM.
Only other consideration is the measurement criteria. Throttle bodies and 4 BBL carbs are measured at 1.5 cm H2O vacuum. If, for the sake of argument, you want as little restriction as possible, then going 10% larger in CFM size will reduce the intake restriction towards (but not to) zero.
For a 383 CID at 6000 RPM, the 52mm TB has flow to spare unless you are super/turbo charged.
For the sake of argument, assume 7000 RPM in a 383 CID with 100% volumetric efficiency.
Result is 776 CFM.
Only other consideration is the measurement criteria. Throttle bodies and 4 BBL carbs are measured at 1.5 cm H2O vacuum. If, for the sake of argument, you want as little restriction as possible, then going 10% larger in CFM size will reduce the intake restriction towards (but not to) zero.
For a 383 CID at 6000 RPM, the 52mm TB has flow to spare unless you are super/turbo charged.
