holley 750 double pumper carb?

Question

i have a 750 double pumper on a ford mustang 302 and its fouling the plugs and a guy at a local ford shop told me its to big of a carb i have e-303 cam gt-40 heads 1.7rr full msd egn. barry grant fuel presure regulator he also told me if i jet it down that it would work fine he said he just done the same thing for a guy and it worked fine,but hes out of town now and i need to no do i need to change the squirters also i have #31 INSTALLED NOW.

Answer 1

if you didn't build this car, then find some-one you trust as a repair person he sounds on track to me
premium operating conditions depend on different system settings for elevation , fuel type,and temperatures .and if the car has sat unattended there would be break-in for it

Answer 2

Try everything your shop recommended. I'd like to suggest the following. The only 302's that ever used the double pumpers were the ones used in road racing in the 60's. They operated in the 5,000 - 8,000 rpm range. You may find company's that offer delayed secondary throttle pick-ups that will allow you to run on the primaries 80-90% of the time. If you're using the MSD ignition there's none better but it's pretty obvious you need smaller squirters and smaller jets. Do the squirter thing first and keep reading plugs. If the plugs are still black drop a couple of jet sizes at a crack to lean it out. Depending on your idle inches of mercury *(vacuum) be sure your power valves are at least stamped with numbers a minimum of two numbers LOWER than your vacuum at idle For instance: If your idle vacuum is 7.5 inches of mercury install both power valves with 5.5 stamped in the side of the sides. This helps to give you a cleaner fuel mixture with the motor while idle. Try these things first. If they do not work find a vacuum secondary 650. You can play with secondary tip-in openings with different variety's of springs. You'll love this Holley I'll guarantee it. 360 dirt circle track Chevrolet motors scream on up to 7,500 rpm's with the double pumper 650's.

Answer 3

I'd go with around a 650 single pump carb. Sure you can jet it down, but you more than likely still have to deal with a super-lean aircharge at higher RPM since you can't turn down the air intake volume and speed to match the lower fuel delivery. It'll more than likely end up falling flat on it's face when nailing it from an idle by just re-jetting, since it's such a big carb. I've ran 650's on many hot small block 350's without any starvation.