Quote:
Originally Posted by av8or32
My Firebird has a 400 Potniac motor/muncie 4sp combo. It has a mild cam, headers, a performer RPM manifold, and a Holley 800 double pumper carb. The problem I'm seeing is it's way too much carb for my motor. I've done the math and I keep coming up with about 600cfm. I'm planning on going to a performer intake and getting rid of the rpm. It's going to be driven on the street and maybe a track every now and then. I know I should use a vacuum secondary carb but I'm torn between the 600 and 750 e-brocks. Thoughts?
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I have set up many carbs on Pontiac 400's and your current carb size is good for your combo.
E- carbs are cheap and will just get you from point "A" to point "B"
If it's running rich now it not because of the size it's because it is not set up correctly and the dist may need some curving.
Test your combo for carb size.....
Connect a vacuum gage to a full source and string it into the car so you or someone riding shotgun can read it while driving.
Make a substained WOT run and see how much vacuum your pulling @ WOT
Vacuum gage should go to "ZERO" if sized right.
If it's too small it will pull vacuum.
Jeff