Technical Having fuel problems

I have a 255 m
cu.in Merc. flathead stock with the exceptions of offy heads and intake with a tpot holly 4 barrel 390 cfm I believe. I have an electric fuel pump but I can only go about 5 miles before I seem to run out gas however gas tank is full and clean and all filters are clean any answers???

 

Are you certain it is a fuel problem then? Have you disconnected the fuel line at the carb to see if it is still pushing fuel? I had a Ford Bronco some years ago that had a bad ign. coil that did that, it had me chasing my tail awhile before I got that one figured out. N.N.

 

Is there a sock filter on the pickup in the tank?

 

Is the tank vent clear? The pump won't work if you can't replace the gas going out with some air coming in.

 

That and cracks or pinholes in the rear hose, pick up tube or plugged vent.

 

I'll suggest checking for proper venting.Try going for a drive with the gas cap off.

 

Rubber fuel line collapsing from suction? This crap they pass on to us as fuel just eats up rubber parts.

 

Any inline filter that needs cleaned?

 

I have always been told most fuel problems are electrical

 

Venting seems to be the problem.Went for a drive with the gass cap off and never quit at all.now what is the best way to restore the vent. Is it possible to drill a couple of 1/8 inch holes below the cap or what/ Thanks guys for all your help--spike

 

Might be better just to get a venting gas cap. I had a similar issue and I used a thermal sleeve around the fuel line from pump to carb. I haven't had any issues since.

 

Yes,go buy a vented cap

 

VENTED GAS CAP!!! I messed with that for the better part of a week before I accidentally left it in my pocket one day filling it up!