I just went from a Weiand Team G single plane intake with a Holley 750 dp to a Edelbrock RPM Air Gap and a 750 VS.
With the Team G/DP, I could go about 2 1/2 hrs on 22 gals of gas with a 5000 rpm max. With the Air Gap/VS set-up, I can go about 6 1/2 hrs on 22 gals and I now get 5200 rpms. That is real time and not speculation with the comparison being made at 3500 rpm cruising .
Both carbs were set-up by Bigs Performance based on my engine specs.
Well my math says that if you had 100 VE your 502 spining 5000 rpms would you 726 cfm. So a 700 or 750 would work for you. If you go to a vacc 2nd carb you will save some fuel. (no squirters) You will see a big reduction in the use of fuel if you always on and off the throttle. If you keep your speed constent, you will really see no diff.
I have a Speed Demon 850 on my ZZ502 w- Legend Pump "a" impeller
Mech secondaries - Not a gas guzzler unless I bury my foot the the gas gage moves faster than the tach
I think you have some tuning issues. Do the secondaries open before the or just after the boat planes? - The power valve is suspect - run a vacuum gage and run a PV # 1/2 the idle vacuum. I don't think a 750 is your answer
I'm running a 750 vac sec on my mild 454. 23', heavy hull daycruiser with a bottom in need of strake repairs, and I get just over 2mpg cruising at 3200rpm with 4 people and gear on board. My secondaries open at 3800rpm, sooner if pulling a tube.
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