When I first acquired my ’53 Le Mans Coupe (with SU carburetors), every time I would go to start it after sitting for a few weeks, I’d have to crank for 20-30 seconds before it would fire.
Finally, I installed an AirTex E8902 6V electric pump along the rear frame, near the gas tank, and inline on the way to the engine driven pump. The E8902 is the lowest pressure pump on AirTex list, I believe it calls for 2.5 – 4 PSI. The pump has isolated ground (i.e., two power wires), so hooking up for positive ground is not an issue.
As most owners know, the fuel line from the tank exits at the TOP of the tank, so I was a bit concerned about priming issues with the pump, but it was no worry.
I provided power to the pump through the ignition switch AND an under dash toggle switch. I only run the pump to prime the carbs if the car has been sitting for a week or so. I turn on the ignition, turn on the pump switch, and wait about 15-20 seconds.. you can hear the sound of the pump change as the fuel bowls fill up and pressure backs up a bit. Then it’s full choke, hit the starter, and the old babe cranks right up on the 2nd or 3rd revolution.
The new AirTex pumps now come with a LIFETIME warranty, and prices have been reduced some 30% from just a couple of years ago. I got this one on Amazon for just about $30. Deal of the century!