Can it be done with the stock fuel tank?

This car has had a intermittent fuel starvation problem I have not been able to solve for about a year now. It is ok when the weather is cool. The problem begins to occur when the ambient temperature goes above 70 and I have driven it awhile. When in wide open throttle the fuel pressure drops and the engine falls off. It is a 68 dart with a 505, cammed so mild it sounds like a stocker when it idles and I drive it daily. I make about one trip a month to the track where it runs 7,70s. Its not that quick so it doesn't seem the fuel demand would be that high.

The entire fuel system is new including the fuel tank and a 1/2 inch pickup. It currently has a holley 110 gph electric fuel pump with regulator set to 7 psi. The fuel line is 1/2 inch from tank to pump and 3/8 from pump to carbutetor. I only run at the track with fuel tank full. I have also tried it with a carter 120 gph mechanical but it has the same problem. I have tried both in series and still have the same problem. The fuel line is routed in the stock location and has to cross over the exhaust system on the right side before it gets to the engine. I cannot find a way to overcome this without running the fuel line inside the car but I do not want to do this. I have the fuel line insulated where it crosses over the exhaust just in front of where the tailpipe arch is located.

This problem has me frustrated that I cannot solve it. This fuel system is the same as I have used on other cars that worked well with no problem. Any suggestions would be appreciated and also I would like to hear how some of you have routed your fuel lines and where you have your electric fuel pumps located.

Thanks for any suggestions.

Roger

do you have a fuel pressure gauge in the cockpit?

Yes I do and I have the fuel pressure set to 7 psi. When the engine lays down the the fuel pressure will drop to about 1 psi or less. However this problem goes away when the weather is cool, about 65 degrees or less.

Since this type of setup has worked for me before (20 plus years ago) and since it seems to be so temperature sensitive I am wandering if the fuels blends available today may vapor lock much easier than before. Does anyone know about the fuels we get today? It seems it might blended different (vaporize much easier) since everything is fuel injected today.

Roger

110 fuel pump seems small to me. how old is it?

that's correct about fuel volatility nowadays. i have a similar combo- 496 in an a body, street/strip. it runs 7.0 at 3500 feet in blazing desert heat. stock fuel tank, carter mechanical pump, 3/8 line, and no fuel delivery problems at all. as a matter of fact, it had no problems with the 5/16 line either! i suspect you've got a problem possibly with your pickup, or with your system configuration. have you tried running both pumps? what kind of filter arrangement do you have?

The fuel pump is about 2 months old with maybe 500 mile on it.

Guys with stock tanks, where do you have your electric pumps mounted?

Thanks,

Roger

Joe Ewing has a 63 Dodge NSS car stock gas tank with a holley blue pump. He runs 10.30's all day no fuel issues. One thing that may help is the 2 carburators on the crossram, twice the fuel already in the carbs vs single 4bbl.

i have mechanical only. i may add an electric if i make more power. what type of filter do you have? where is it located?

How far back into the tank does the 1/2" pickup go - enough to insure it doesn't get uncovered on acceleration? Where is the fuel filter in relation to the pump, and how close is the pump mounted to the tank?

Personally, I do not trust any in-car mounted fuel pressure gauge. The positioning of those isolators can be tricky, and have heard guys say they get flaky readings from them (assuming you are using an isolator, since the gauge is inside the drivers compartment.)

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The fuel pump is about 2 months old with maybe 500 mile on it.

Guys with stock tanks, where do you have your electric pumps mounted?

Thanks,

Roger

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My pump is mounted at the rear of
the right rear sub frame behind the fuel sump. It is fed by a #10 hard line and from the pump it is a # 8 to the regulator in the front. It sounds like you are running out of fuel, my car started out with a Magna Fuel 275 pump and I ended up having to change it to a Magna Fuel 300 due to running out of fuel from the starting the line to the finish line according to my wide ban O2 sensor. The car ran 10:73 at 127 mph running out of fuel and didn't indicate that it was lean during the run I don't have a fuel pressure gauge that I can see during the run also It also sounds like the current system is marginal now and probally won't get better with age unless you upgrade the pump or find out if and what is restricting the fuel flow to the motor. I was taught that if the fuel pressure drops during the run you need a beter fuel delivery system I have seen cars go in the low nines with a single Holley blue pump and pick up three tenths and 4 MPH by replacng that pump with a bigger pump, that was a NOS car that didn't miss or burn up spark plugs during those runs He treid jetting the car up two jet sizes at a time five times(10 jet sizes ) and the car ran within .05 ET and .25 MPH on all five runs My is get a better pump, a lot better now so you won't have to do what I did, buy a good pump twice