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I just want your opinions on what would be a better carb for a 390 with a performer intake in a Thiokol Snow Groomer, a 500cfm or a 600cfm 4v. I am looking for good off idle torque and max rpm's will not be excessive... Most people seem to think the 600 is better for street applications but I am leaning to the 500 to keep things as crisp as possible. I just don't want to be under-carbed. What would the guys at the bar say when they find out I only have 500cfm... Thanks guys.
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More specifically this Edelbrock Carburetor: Thunder AVS, 500 cfm, Square Bore, Manual Choke, 4-Barrel, Air Valve, Single Inlet. I like the idea of being able to tune in the secondarys.
Bump for you, hopfully someone who has used a 500 4v & 390 can can jump in on this.
From a purely technical standpoint, if we assume 80% volumetric efficiency, a 500CFM carb runs out of air & fuel on a 390 @ 5500rpm. With a 600CFM on tap, we are looking at 6650rpm.
Personally, I have a 600CFM Holley 4160 that I previously used with the 302 in my Mustang that will find a new home sitting on top of the 390. Throttle response on the "little" 302 was fine but it was definitely too much carb. I expect response on the 390 to be just fine... after I get it dialed in. I also have a 600CFM Autolite 4100 I plan on playing with, but it needs some work. Secondary tuning will be key. I'll never spin my 390 up to the 6650rpm, but that shouldn't matter with a vacuum secondary.
Seeing as you are running this thing in the snow, I'd be very careful with the jetting. Depending on your temperature differential between winter and summer, and things can get interesting. Tune it now and she will run lean come winter time when the air gets cold and thick. I have zero experience with the Edelbrock/Carter carbs, but I know there are formulas out there for up-sizing and down-sizing Holley jets based on altitude and temperature.
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