Fuel Pressure // Real Tech Question

[big-boss]

Seems like when I try to adjust my fuel pressue I really don't have control using my rear of the carburator mounted Mallory fuel regulator. I have the stock Kirkham electric fuel pump running into a carter mech fuel pump.
I cannot seem to raise the pressure.
Is there a regulator in in one of the fuel pumps I should take out? I can only raise it to a little over 7.5.
Everything runs fine I am just screwing with it.

[CobraEd]

most mechanical pumps are set to about a max of 7.5.

Also, if there is not a regulator in the electric pump, it could blow out the rubber diaphram in your mechanical pump and dump TONS of gas into your crankcase.

.

[PANAVIA]

Agreed - just run the electric OR the mechanical. -

[ERA Chas]

I have run a Holley Red 6.5 psi electric feeding the Carter mechanical you have for a long time-trouble free. Find out from KMP what their electric psi is. The Carter is about a 7psi and the key is to not feed it more than that. You're running right at the high limit of 'smart' at 7.5psi-6.5 is sufficient up to 700HP or so.

[Excaliber]

Mine runs about 7-7.5, I've always thought that was a bit on the high side myself. I just haven't gotten around to buying a pressure regulator to REDUCE it from 7 to 5 or 6. Like you said, just screwing around. IF 5 psi would do the job, terrific!

[Ron61]

I had the Holly Blue pump which put out 14 pounds so I had to put in a regulator. I kept mine set at around 6.5 to 7 pounds and never had any problems. Actually I think Holly recommended 5.5 to 7 pounds on the carb that I had built. I never used a mechanical pump so that didn't affect anything in my fuel set up.

Ron

[PANAVIA]

Base Kirkham electric is the Red' labeled Holley @ 97 GPH.

[RICK LAKE]

Big Boss 6psi to 6.5 is the limit on most carbs. Unless you car is having vapor lock after driving, having 2 pumps can cause a problem like said above. If your car has a return line off the regulator. you should be able to adjust it down to 6 psi. Are you getting black smoke out of the motor on startup or around a turn? If not you might want to leave the setup the way it is. If it was my car. I would remove the mechanical pump and just run electrical and cap off the pump or remove it. Put a bypass connection in there that if your back pump goes you could use the front one to get home. Return line is also important for keeping pressure steady and not getting spikes and having the needle pop off the seat and push too much gas into the carb and possible motor. Electric pumps don't like to be deadheaded without sensors to have the pump increase and decrease pressure. Rick L.