Thread: what carb to use

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I am building a 408 small block chevy with blower pistons & h-beam 4340 rods. a blower cam from 2200 to 6000 rpms. i am putting a b@m 144 blower on it. i have AFR 195cc heads & I need to know what carb to put on it. some people told me a 750 some told me a 850 some told me it needs to have 3 circuits in it. I would like some imput on this from some people that have built blower motors please. thanks.

Originally posted by randbchevy
I am building a 408 small block chevy with blower pistons & h-beam 4340 rods. a blower cam from 2200 to 6000 rpms. i am putting a b@m 144 blower on it. i have AFR 195cc heads & I need to know what carb to put on it. some people told me a 750 some told me a 850 some told me it needs to have 3 circuits in it. I would like some imput on this from some people that have built blower motors please. thanks.

The size of carb(s) or CFM required for a given application can be calculated by the following formula A: {(CID x RPM) ÷ 3456} x {Boost ÷ 14.7) + 1} = CFM required. The amount of CFM required will determine carburetor size and quantity. If you try to use a carb with less CFM than required, performance and economy may be greatly reduced.

408 x 6000 = 2448000 x 6 = 14588000 / 14.7 = 992380 +1= 992 = CFM needed

randbchevy you didnt say what boost you was gonna run so i used 6 lbs. here, which you would need somewhere around 1000 CFM using this formula with 6 lbs of boost. go on the high side to start with.