Fuel Starvation?

[SLC Duster Dude]

My 73 Duster was originally a 6 cyl car but now has a 360 mated to a 727. I believe the trans to be mostly stock but the engine has the Edelbrock performer carb (1406), cam and intake. It also has roller rockers and ceramic coated headers along with the J heads. I just switched out the 2.93 gears for some 4.10's and when standing on it in Drive I notice it start to lay down in 3rd gear around 4500 rpm. It doesn't feel like it's out of gas, but it stops pulling and you can feel it just sort of lay there. It will pull to 5500 in first if I shift it but then it stumbles by the time I shift to third and the RPM's start to climb. The fuel pump is upgraded from stock but I don't know the specs are on it, however, it is pulling from the tank thru the stock hard lines which I believe are 5/16". Would I benefit from running 3/8" line all the way to the fuel pump from the tank?

 

[Kiwicharger]

Gudday Mate,
You have basically the same set up as me. I run 3/8" line all the way through. I'm running a Carter electric pump mounted to the rear under body directly in front of the diff. I have a professional products inline filter after the pump and before Holley regulator. You will definitely benefit from the larger fuel line.
I'm also going to run a return line when I pull the motor for repainting. Two points being that with a return line installed, I can opt for an EFI fuel system in the future if I want and also the electric pump will run quieter.

Best of luck
Regards Pete

 

[KnuckleDuster]

My 73 Duster was originally a 6 cyl car but now has a 360 mated to a 727. I believe the trans to be mostly stock but the engine has the Edelbrock performer carb (1406), cam and intake. It also has roller rockers and ceramic coated headers along with the J heads. I just switched out the 2.93 gears for some 4.10's and when standing on it in Drive I notice it start to lay down in 3rd gear around 4500 rpm. It doesn't feel like it's out of gas, but it stops pulling and you can feel it just sort of lay there. It will pull to 5500 in first if I shift it but then it stumbles by the time I shift to third and the RPM's start to climb. The fuel pump is upgraded from stock but I don't know the specs are on it, however, it is pulling from the tank thru the stock hard lines which I believe are 5/16". Would I benefit from running 3/8" line all the way to the fuel pump from the tank?

How close is your fuel line to your header collectors?

You are going to need a fuel pressure/ vacuum guage, about $20 at any auto parts store and a damn good investment regardless of your issue.

How old is your fuel pump? Filter?
Fuel tank?
You need to find out what fuel pump you have, post a pic of it if possible.
Rubber fuel hoses new and in good shape?


It could very well be ignition related, BUT start with fuel first so you don't get overwhelmed.
Bigger fuel line won't help you if heat is your problem.
Throwing money at with 3/8 line ( and sender ), bigger mechanical or electric pumps, different carb, etc. Will get frustrating real fast.

 

[d55dave]

Yes. A bigger line is absolutely beneficial especially with an engine driven pump that sucks through the line. Modern fuels with ethanol vaporize more easily under these conditions. This is most apparent under high fuel demands....the highest of which is winding out in third.

At the very least you need to pull the pickup and ensure that the old factory sock on it is not plugged.

 

[SLC Duster Dude]

Attached are pics of the fuel pump and the line that runs from the pump to the carb.

 

[TrailBeast]

From the look of those lines and the lower gasket on that pump it doesn't surprise me one bit that you are having possible fuel issues.
Likely you are only getting fuel foam.

 

[SLC Duster Dude]

I just replaced the fuel line to the carb. I guess I'll look for a rebuild kit for the pump. Until I took the pic I couldn't even see the gasket on the pump.