Join Date: Mar 2002
Location: Austin, TX, USA
Re: Carb and intake question
The 600cfm rating is appropriate for a street driven SBC350 if the carb is a square bore carb (as most of the Holley carbs are). If you use a spread bore (like the Q-jet or Edelbrock) then you can affort to go a bit higher. As for intakes, on a street motor, just about any dual plane intake will work. I run the Edelbrock Performer RPM.
For square bore carb sizing, this formula will get you in the ball-park at 100% volumetric efficiency. In reality, the VE will depend on the heads, cam and other variables. 80% is realistic for a stock engine, 90% or higher can be obtained with the right heads and cam (though the power band is likely to be much more narrow). In any event, multiply the result from the formula by the VE (i.e. multiply by .80 if the VE is 80%).
CFM = MAX_PRM * DISPLACEMENT / 3456.
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI