Hello everyone, I'm building a 331 with AFR 165 intake runner heads, mild cam,dual plane manifold, 10 to 1 flat top pistons and a Hughes 3000 stall converter. My question is; what size carb should I use and should it be vacuum or mechanical secondaries ? Is a 3000 stall speed converter high enough to use a double pumper with out the engine bogging down when mashing the gas pedal from a stand still? The rear end has 355 gears and the 15 inch rear tire diameter is 27.250. Thanks, Joe
I would lean towards something close to 700 cfm and no less than 650. With a 650 you will probably have to re-jet it to accommodate the intake and heads. With an auto trans I would shy away from a double pumper although I have seen them used on several automatics.
I've got a 650 on the 331 in my mav, mechanical secondary double pumper. Throttle response is excellent.
With that gear and tire, I'd go with a VS (750 Holley with ford kick -down) UNLESS you know how to really tune a Holley. If so, a 650 would give great results when properly tuned. Myself, I run a 750DP on the Comet and a 700DP on the Cougar, but both are stick with gear.
I have a 650 hp double pumper mechanical secondary on my Maverick and also had the same on my Comet Mav is a 347 Comet was 302 and both ran great with a little tuning Big difference in motors though. Both got great fuel mileage.
Thanks everyone! I was thinking about getting a Quick Fuel Q650-PV with vacuum secondaries no choke or choke tower. I don't need those here in Florida. Another person said that from a stand still start I would need a 4000 RPM stall converter to be able to stomp the gas and not bog down if I used a double pumper. With slapper traction bars ,15 inch tires with 9.5 inch tread I don't think I'll be able to get the tires to break loose to bring up the RPM enough to get to 4000 rpm .Although I can get the tires to chirp when shifting into second gear with my 302 when running hard. Maybe I'm over thinking this but carbs are expensive and I want to get it right the first time. I rather be to small then to large. Joe
That is the exact carb that I have on my Maverick with 347 and a really low stall I think it's only 1800-2000 rpm and it works great. It had a stumble from start but after tunning it works great no stumble and also gets great gas mileage. So with that kind of stall around 2500-3000 you should have a great setup.
That carb will be do damned fine for your "mild cam" combo. And not many people use 4k stalls with a mild cam since the converter eats into and diminishes usable lower rpm range operation due to slippage. The smaller cam just can't take full advantage of the now narrower power band used to accelerate the car. 3k should be plenty of stall speed with that gear and engine combo. Would be a fun daily driver if you ever wanted it to be. Not to debate the merits or shortfalls of any particular carb size for this combo.. but it's a very well known engine builders rule that a dual plane manifold makes a carb seem smaller to an engine(simply because it only draws on half the carb).. and a single plane makes it feel bigger(because it simultaneously draws on all barrels and creates a smaller pressure drop across the booster to act as if the carb sizing were larger than it really is). Add a big cam and heavy right foot and people quickly think the carbs are too big when they just don't know how to recalibrate the fuel curve to fit a specific combo of parts and vehicle weight. Light car with healthy intake system, 3,000 rpm stall with 3.55 gears probably won't be bogging down very easily. If staying with the dual plane manifold.. I'd seriously consider the 750VS version of the above mentioned carb. Leaves you a bit more latitude for future upgrades. Especially when you decide to run a bigger cam and more gear. And eventually you probably will want a faster bullet like the rest of us.
EXACTLY! If you are serious on a carb that will work now AND later, call Patrick @ Pro Systems and he can set you up.
