jerry pearson

I am building a carburated 1991 SBF and I am working on the fuel system. I have a few general questions.


Is the stock in tank fuel pump acceptable?
Is the stock diameter supply line acceptable?
I will run the supply and return lines at the tank but what is done with the evap (3rd line) at the tank? Just plug the line? Vent the line? Remove the unit from the tanks and plate the hole?


Thank you.

epantoja

I used the stock fuel lines with my Ford conversion but I’m using the stock Ford fuel injection system. I believe if you’re using a carburetor, you’re going to need a fuel regulator to reduce the fuel pressure of the stock Miata fuel pump. It puts out about 40 psi and I think for a carburetor you don’t need more than 7-10 psi. Otherwise your carburetor float needle will never seat. As for the vent line, I just capped mine off with a rubber vacuum cap at the outlet in the engine bay.

engineer

Hi,

To answer your questions,

FUEL PUMP: If you will be making over 300hp on the engine ( I hope you are) then YES upgrade the in tank pump (its likely old anyway). I would go walbro 255lph..cheap and reliable...will supply up to 500hp.
FUEL LINE; If you will be making over 300hp on the engine ( I hope you are) then upgrade the SUPPLY fuel line to 3/8 (its 5/16). You can use the original 5/16 line for the return line

You MUST run a regulator as you are running a carburetor. The fuel pump will supply 80 psi of pressure and the carburettor only needs 6-7 psi. So you have to use the regulator otherwise you will damage the carb floats and needles.

For the Evap lines you should keep them all in place as they do an important job of removing fuel smells. dont touch any of them simply reconnect the vacuum line form the purge solenoid back to the intake manifold for vacuum and the use a "timer circuit" to open the valve for 2-3 seconds every 5-10 minutes to suck any fumes out of the tank and into the charcoal canister and engine.

Another old thread...I am very bored at work today...

cheers