Carburetor CFM

BigDave

BigDave

Active Member
Supporting Member
I have a 440 dodge in a 52 ford

I have two choices for carburetor

Both Edelbrock 1 is 600 cfm
The other is 750 cfm
Mathematical the 600 is border line
Motor is basically stock 1978 with a Edelbrock dual plane manifold and headers
Which do you think would be a better choice

Dave
 
I would go with the 750. The secondary air valves open as vacuum demand builds, so there's no downside to using a bigger carb. GM Qjets were available in two ratings, 750 and 800 cfm. They used the 800 version on all the stock big blocks.
 
Rpm is crucial here and a 78 engine is going to be very mild and most likely from a motor home hence low end cam etc . GFaRT is correct in some respects Gm did use large carbs but with smaller primaries which is needed for airspeed - air fuel mixing at lower speeds and secondaries that can be set for opening . Do you know what carb it came with ? Are these used carbs ? Edelbrocks are very settable carbs and I'm sure either could be made to work well with proper tuning . PS My 408 ci huge cam aluminum head stroker calls for a 620 cfm on a carb size find chart because of it being built for 5500 rpm max . If I input 6500 rpm the size goes up by 100 cfm .
 
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