CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Electric Fuel Pump vs mechanical on '71 Mach 1

I just acquired a '71 Mach 1 and noticed an electric fuel pump wired up in the trunk behind the left wheel well. There is a toggle switch wired to the center console. Is the electric pump the way to go or would the mechanical pump be sufficient for a 800CFM 4 barrel carb? not sure if its working properly as I had some carb problems that I am taking care of as we speak. Also, would I need a pressure regulator for the electric pump?

What kind of engine is in that car to require 800 cfm? That large a carburetor needs a significant fuel pump and the help of some veteran muscle car mechanics to get it set up properly. 800 cfm wouldn’t work well unless the engine was >7L and operating at near 7000 rpm.

it’s a 4781 holley (850cfm) on a 351 Cleveland…What carb do you suggest?

George…a 450 Holley will work just fine for street performance. I would use the electric fuel pump if the pressure is adjustable for the carb that you are using.

Yes, a 450 cfm would be a good match at rpms up to 6,000 on a 351 engine. That 850 will make the engine fall on its face above 1/2 throttle.

Yes, way to much carb for that. I ran a 850cfm on 383 Mopar. It was great at the track, but not good on the street. I ran a 600cfm on the street motor. I did a lot of work on the motor to run a 850cfm carb. I would keep the electric fuel pump and use a regulator.

The electric pump was probably installed to overcome vapor locking problems in hot weather…Is the mechanical pump still in the fuel delivery circuit or has it been bypassed?