Another running out of fuel question

[Saltshaker]

My 428 has a carter mech pump and I run out of fuel in 3rd gear around 5k ....motor has ported c4 heads and a comp 282s cam rpm intake etc...I added a carter 70gal pump behind it and now pulls to 5500 but then slows down ....it should pull past 6k. Fuel line is 3/8 all the way. I'd like to get it fixed before Beaver Springs....suggestions?
Jon

[mbrunson427]

Is the float level on the carb(s) adjusted?

[Saltshaker]

Floats are level. I was wondering if the Mech pump was interfering with the electric pump?
Jon

[Heo]

My 428 has a carter mech pump and I run out of fuel in 3rd gear around 5k ....motor has ported c4 heads and a comp 282s cam rpm intake etc...I added a carter 70gal pump behind it and now pulls to 5500 but then slows down ....it should pull past 6k. Fuel line is 3/8 all the way. I'd like to get it fixed before Beaver Springs....suggestions?
Jon

iI have the same setup minus the electrical pump a 400 though (390+.060) no fuel problem

[e philpott]

Floats are level. I was wondering if the Mech pump was interfering with the electric pump?
Jon

Would it be hard to by-pass the pump for testing purposes ?

[Heo]

How is the ventilaton on the tank. Try running without the fuel cap

[Saltshaker]

Going to bypass the mech pump and see. Tank vent is a 3/8 hose. Motor has no problem pulling 7k 1st gear.when it was chassis dumped with the hood open in 4th it pulled 6k
Jon

[Posi67]

Where did you locate the electric pump? It needs to be at the tank to work properly. I ran a similar setup years ago and it worked fine without the electric just cruising but the mechanical wouldn't pull through the electric if I was getting on it and forgot to turn the electric on. Another possibility is the pickup in the tank.

[Saltshaker]

Pump is located at the tank. It is plumed with a check valve so I can run the mech carter pump with out the electric pump. There was a improvement when I added the electric pump but not what I was expecting.  thoughts ; air filter is. 8.25x2” k&n and wondering if it’s to small! Also, running 38 deg timing with 10.1 comp on 93
Jon

[Posi67]

Sounds like you're doing the right things. I can't comment on the air filter since I never run one but that's an easy thing to eliminate. In my experience, when I forgot to turn on the electric the car would sputter then feel like it shut off about the top of 2nd gear. This is another one of those  "is it fuel or something else" problems. Might want to check for bad or broken valve springs.

[fryedaddy]

i was running out of fuel and nosing over when i hit high gear.turned out my fuel lines are in front of my tank and all my gas was flying to the back of the tank under acceleration and causing me to run low on fuel about the time i hit high gear.now i wont run it hard unless i have more than a half a tank.i may spin my fuel cell around where the lines will come out the back.that would force my last little bit of gas to the lines. just a thought.

[chris401]

My 428 has a carter mech pump and I run out of fuel in 3rd gear around 5k ....motor has ported c4 heads and a comp 282s cam rpm intake etc...I added a carter 70gal pump behind it and now pulls to 5500 but then slows down ....it should pull past 6k. Fuel line is 3/8 all the way. I'd like to get it fixed before Beaver Springs....suggestions?
Jon

Heo had a good suggestion. That will find a restricted tank vent. Also check the flair where your steel line fittings screw in. They could be too small. I have had a couple of tanks opened up to 7/16" and adapted to 3/8" lines.

[Falcon67]

Also check where the lines come out of the tank - when I used the stock tank, I discovered the "5/16" feed line out of the sender unit was actually necked down to around 1/4" where it passed through the mounting plate. 

[6667fan]

Is it known what your psi is at 5500 or whenever it stops pulling? What type of carb? Some of the QFT carbs perform best with 6 plus psi under load.
JB