Fuel overflow

[Phillipb71]

Early 70 350 w/ vortec heads stock cam and Edlebrock carb.. ran for 4-5 months and started overflowing fuel out if top of carb/ vent. Put new carb on same thing. Pinched fuel line from mechanical pump and blew out the pump weep holes. Bypass mechanical with an electric pump4psi with 3rd carb same thing. Doesn't overflow sitting cranking over as soon as is starts and runs it overflows.. replaced mechanical pump and put fuel pressure gauge it was 8psi before it blew out that pump also?????? Help

[rspears]

I agree that a fuel pressure regulator is a great idea, but your post makes it sound almost like you've got an OEM electric fuel pump in the tank that didn't get unhooked when you changed over from an EFI engine to a mechanical pump and carb! Yes, that sounds crazy but then going through 3 carbs and several pumps is kind of a crazy deal, and not cheap!

[Phillipb71]

The pump is in the tank but the relay and the fuse have been pulled. The pump in tank isn't running.

[Phillipb71]

We are going to get away from the Edlebrock and put a Rochester on with the 4 psi electric and see what happens. I feel like we are chasing 2 separate issues the fuel out of carb and why the mechanical blows seals when the line is pinched off

[rspears]

We are going to get away from the Edlebrock and put a Rochester on with the 4 psi electric and see what happens. I feel like we are chasing 2 separate issues the fuel out of carb and why the mechanical blows seals when the line is pinched off

Do you have an in-line pressure gauge on it to verify the pressure at the carb? It's a cheap item, but priceless information to know for sure, and not trust equipment specs. https://www.speedwaymotors.com/Liqui...SI,293991.html

[Phillipb71]

Yes electric is 4psi the stock mechanical was a hair under 8psi

[36 sedan]

The pump is in the tank but the relay and the fuse have been pulled. The pump in tank isn't running.

JMHO, an tank electric fuel pump exits the top of the tank and it usually doesn't work well pulling fuel through them up hill by a siphon type pump be it mechanical or electric. Siphon fed mechanical or electric pumps are usually sourced from the bottom of the tank allowing fuel stacked in the tank to aid in the siphon feed to the pump.

I'll bet Roger is correct, the in tank pump is running when the motor is operating, as this would explain the multiple carb and pump issues. Your pressure maybe lower while cranking if the tank pump is not on at that time, then once running I'd bet it's coming on and the pressure jumps up flooding it. Possibly someone hooked something up that was disconnected before.

Pinching a fuel line on the exit side of a pump will blow the seals/diaphragm unless it has a pressure bypass.

8psi is too much pressure for a carb. IMHO, no carb needs more than 5psi. If 5psi is not supplying enough fuel to the motor, your line size is undersized or restricted.

JMHO, I would use the in tank fuel pump with a bypass (return line) regulator near the carb set at no more than 5psi. And again, JMHO, the only thing wrong with Edelbrock carbs is people misunderstanding them, once adjusted and tuned correctly they will perform as well as any other...

[rspears]

I was going to say earlier that the OEM circuit for an in tank pump has a bunch of interlocks, like initial run to pressurize, safety interlocks, oil pressure interlocks, etc, etc and they are all but silent when running due to being submerged, which is by design. Trying to draw through the stock pump with the suction of another pump, either mechanical or electric is a bad idea. I expect you've still got a power source to the stock pump, and you need to either use it or drop the tank and remove it, replacing it with a proper suction line.