Help With fuel ??

Dutch65mustang · Mar 26, 2010

At the moment i'm running a blown 331 engine with a mechanical fuel pump with boost enrichment on a 650 cfm blow through QFT holley carb.

Problem is that the car has really low fuel pressure of 3 psi and it doesnt run good also (think the pressure is way to low).

Thinking about ditching the whole mechanical fuel pump and go with a electric pump with fuel regulator.

What do i need ?

Fuel pump
Backoff plate for engine
regulator
relais

Is that it ? or should i need more to switch to electric pump ?

Also wich one should i take, there are so many pumps on ebay and wich fuel pressure would be best to start with, 7-9 psi i read for holley's ?

Need to order everything abroad so need to get the right stuff and in one order (shipping costs...)

Thanks !

rbohm · Mar 26, 2010

low fuel pressure is an indication that you have a fuel volume issue, as in not enough volume. you should be running at least 3/8" fuel line and 1/2" would be better from the tank to the carb. you dont have to step up to an electric pump just yet, try using a carter competition mechanical pump like the cup car used to use back in the day of 700hp big blocks.

another thing you can do is use a good electric pump located near the tank, and the stock mechanical pump to limit fuel pressure without using a regulator. if you choose to use just the electric pump with a pressure regulator, run a return line that is one size smaller than your feed line. for instance if you use a 1/2" feed line your return line should be no larger than 3/8".

gtss · Mar 26, 2010

that should be all you need to go electric, I run one on mine, naturally aspirated.I beleive anything over about 7 psi will push the needle off the seat in the carb.

pay attention to where you mount the pump, most electrics like to push fuel rather than pull

can you not just replace the mechanical one with a better mechanical??
or would you prefer electric?

hope it helps
gtss

Dutch65mustang · Mar 27, 2010

Thank you for the replies, the feed from the tank to the pump is stil the original line, think i'm going to replace that first to see if it helps anything.

I'm running a "beter" pump than original, it was included with the supercharger kit, but i dont have much confidence in it.

When it was idling sometimes the fuel pressure drops to about 1 to zero psi .

i've never seen it go higher than 4 psi, that should be way to low for my engine setup i guess !

I'm not particular into electrical, but i want to have everything as it should be, the engine have cost me alot and i dont want to spare money on the last things such as the fuel delivery etc.. If mechanical is good enough fine i stay mechanical but if electrical is beter for the engine and power yes than i switch to that.

rbohm · Mar 27, 2010

Dutch65mustang said:
Thank you for the replies, the feed from the tank to the pump is stil the original line, think i'm going to replace that first to see if it helps anything.

trying to feed 450+hp through the stock 5/16" fuel line is line trying to run a marathon while breathing through a soda straw. you definitely need to size up your line to 1/2".

Dutch65mustang · Mar 27, 2010

Clear, first thing this week going to upgrade the fuel line then !

The pickup in the tank, should i also change that and weld a bigger outlet on it ?

rbohm · Mar 28, 2010

yes you do want to enlarge the pick up tube as well.

Dutch65mustang · Mar 28, 2010

Ok

Going to work on it this week

Help With fuel ??

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