we have a 73 two door mav with a 30 over 302. it's got stock heads, stealth intake, long tubes, and a mild cam (484 lift and 213 @50 duration) it's getting a set of afr heads, better converter, and some 3.50 gears after christmas. i'm thinking a 600 cfm holly four barrel with vacum secondaries. any thoughts?
Which Carb? As it sits now, the 600 dbl. pumper Holley is a good one. The after XMAS mods would probably stand a 750 dbl. pumper. Your cam would warrant a change if you are to utilize the potential of the new heads and converter. The Edelbrock carb is a good one for out of the box performance but the Holley will give a bit better seat of the pants performance but are a little more difficult to tune in sometimes. Just a dimes worth of advice, get all the engine and rear gear mods done first so that you can give that info to the converter mfg. He will be able to calculate what stall would work best for your application. I myself at one time just bought a converter over the counter and thought it would stall at their advertised numbers(2800) would never get above 2200. Not enough engine etc. Good luck as always.
I think it's safe to say your options are wide open! Some people prefer the double pumpers, they're more for racing apps, while the vacuum secondaries will get you better mileage around town. Old guy is right, you'll probably want a bigger cam with those heads. I do have to disagree on one point (even though i know he knows more than i do), and say that i don't think you'll need bigger than a 650 (perhaps a 650 double-pumper?). Depending on compression, and all that. PERSONALLY though, i think 750's are a little too much for anything but a radical 302 at a low elevation. (There's a guy in town with a blown 396 in a '69 camaro that makes ~800rwhp (SAE) and he just uses a single 750dbl. pumper, of course i live at a high elevation)...If your engine was operating at 100% VE it would still only be able to pull about 600cfm of air, which is why i think a 650 would be fine. Personally i have a Demon and i am happy with it, although the only reason i got that instead of a Holley is because i got a good deal on it I don't really like Edelbrocks, i've heard a lot of complaints although the design is actually better and they're easier to work on.
I would go with a small carb 650 vac 2nd for the street would be good even with the AFRs Holley would be a good choice though all of use has our opinions.Im running a 750 vac 2nd with my set up i think its wasting gas even though theres no boggs hesitations or anything.im going to AFR 185s and very radical solid cam then ill be happy with the 750 until then i could be running a 600.just my thoughts.
Just thought i'd pass something along though: If you do go with a 750cfm, DO NOT get an Edelbrock. The reason i say this is that a friend of mine had a 750 edelbrock on a 350ci bike--he had endless problems with it. When he called the edelbrock tech support they quietly suggested that if he needed a 750cfm he might want to consider a brand "H" carburetor....
