High Perf. Mechanical vs Electric Fuel pump

[70chall440]

I used to run a low end Holley electric pump back by my tank as a "pusher" because my Challenger sits a lot and it was always such a pain to get it started after storage. I removed it because I was having electrical issues where the battery would go dead even after driving the car. I got it into my head that the pump was putting a large draw on the battery; however after I removed the pump I figured out that the battery sucked and the charge wire on the alternator was not even close to being tight. I might put it back on as it is nice to allow it to pump fuel to the mech pump prior to starting.

[cudabob496]

I've read that for a fuel pump, flowrate is equally as important
as pressure.

If you are running out of gas at the end of a quarter mile, you can also
had bigger bowls to your carb.

[JMB340Challenger]

Can I use a mechanical pump with 3/8 fittings with 5/16 fuel line? I realize my flow will be only as good as a 5/16 line, but I'm trying to pace my upgrades as money allows.

[dodj]

It may be as simple as your fuel filter not being up to the task. At WOT it may just not be able to allow the fuel to flow fast enough to keep the bowls full, and you are slowly losing fuel bowl level during your run. 

[70chall440]

Can I use a mechanical pump with 3/8 fittings with 5/16 fuel line? I realize my flow will be only as good as a 5/16 line, but I'm trying to pace my upgrades as money allows.

Yes you can definitely adapt a 3/8 to 5/16

[70chall440]

It may be as simple as your fuel filter not being up to the task. At WOT it may just not be able to allow the fuel to flow fast enough to keep the bowls full, and you are slowly losing fuel bowl level during your run. 

  You also want to check float levels; for street driving it isn't as critical but if it is on the low side to start with, at WOT it could be emptying the bowels faster than they can fill up if they are starting low. The filter is a good place to look, many are very restrictive.

[JMB340Challenger]

Yes you can definitely adapt a 3/8 to 5/16

Ok cool, just wanted to make sure the 3/8 orifice in the fuel pumps wouldn't be trying to draw more than can be supplied by 5/16 line and damage the pump.

[70chall440]

No, it will be fine.

[roadman5312]

                   I remember a tip an old timer gave me back in my drag racing days.  Put a couple large in line fuel filters in line up by the carb(s).  preferably above the level of carb inlets.

[70chall440]

Can I use a mechanical pump with 3/8 fittings with 5/16 fuel line? I realize my flow will be only as good as a 5/16 line, but I'm trying to pace my upgrades as money allows.

know the feeling.

[brads70]

                   I remember a tip an old timer gave me back in my drag racing days.  Put a couple large in line fuel filters in line up by the carb(s).  preferably above the level of carb inlets.

That's similar to what I was thinking..... what about a fuel log between the carb and fuel pump?

If your going to consider an electric pump DON'T get a Holley style, they are crazy noisy!    I have a Mallory pump and it's MUCH quieter.    These are all bandaid solutions for not having a big enough fuel supply line though.

[mopar jack]

Reading through this thread I got to ask did you race this combo before and did it run ok before? Not knowing your  engine specs  the motor could just be floating valves at 6000 rpm or if you have a vacuum secondary carb it may not be opening at the top end of the track. I would hope it's not lack of fuel cause running lean can cause serious problems.

[JMB340Challenger]

Reading through this thread I got to ask did you race this combo before and did it run ok before? Not knowing your  engine specs  the motor could just be floating valves at 6000 rpm or if you have a vacuum secondary carb it may not be opening at the top end of the track. I would hope it's not lack of fuel cause running lean can cause serious problems.

It pulls great through 6000 in 1st and 2nd gear. It's not quite making it to 6k in 3rd... It's closer to 5000 at almost the 1/8th mile when it loses power. From there it's an easy evening drive through the traps lol. Good thought though, thanks for the input!

[cudabob496]

                   I remember a tip an old timer gave me back in my drag racing days.  Put a couple large in line fuel filters in line up by the carb(s).  preferably above the level of carb inlets.

would reduce pressure

[YellowThumper]

would reduce pressure

X2 on this.
And functionally a log (or fuel filters) above the carb may work but you now run the risk of fuel draining from it over filling bowls and elsware.

My 2c is to install a pressure gauge. Low cost option that will show difinitively if you are losing pressure. Pull pick up tube and ensure sock is not clogged. No cost there. Purchase 3/8 pick up tube for the tank. Now you have a new gasket to use with the option to go larger in future.
If sock is clean get new mechanical high volume pump. Test again. If still losing pressure at top end. Change pick up tube and remaining feed line.
Low dollar options first then work your way up.

Another thing mentioned was carb setup. The lower gears of 1st and 2nd will not load your engine the same as the higher 3rd gear will. Test different jetting and see if anything changes. Issue could be there in all gears but masked by the higher gear set but lower load.