I have done several searches and am having trouble coming up with consistent information. I am doing several modifications trying to clean up under the hood for bigger headers, and other miscellaneous upgrades. Part of that is getting rid of the mechanical fuel pump, for an external electric pump. I have already purchased and installed Summit's G3146 pump. It moves 35GPH at less than 9psi. (After installation, the pump runs, but moves NO fuel) Called Summit to request an exchange, and after going through the steps the guy with their technical support team suggested (based on my application) a pump that moves more fuel. The next step up appears to anywhere from 60 to 95 gph.

My "build" - 350 GM crate engine. Comp cams .495 lift, 110* lobe sep, edelbrock rpm intake, and Holley 650 carb. Still running HEI Distributer with vacuum advance. 3" exhaust. - Never had it on a dyno, so estimating hp is pretty tough.

What is everybody's experience with these style of pumps, similar to the G3146? Our biggest hurdle (in my opinion) is where to mount the bigger pumps.

Opinions?

 

A Carter M6626 mechanical pump is all you need. It is an upgrade from stock and costs less than $20.
http://www.ebay.com/itm/Mechanical-F...FZTbN7&vxp=mtr
I can't see how adding an electric pump plus the wiring will be any "cleaner" than the block mounted mechanical. You are supplying a QJet carb. You can't go over 6 psi MAX at the carb. So you will also need a regulator. And it should be a bypassing type that sends the extra fuel back to the tank.

Did you prime the electric FP? Did you get the IN and OUT backwards?
Where did you mount it? Electric FPs PUSH fuel better. If you mounted it in the engine compartment, then no wonder why it does not pump - it's a long way to try to suck the fuel all the way from the tank.

To answer your question about how much fuel is needed, the general formula is 0.5lb of fuel per HP per hour. Gasoline weighs about 6# per gallon.
So if you were making 400 HP, then you would need to supply 33.33 gal/hr at 6psi at WOT.

 

Moving the fuel lines for the new headers was the initial reason for opening up the fuel system. My fuel lines were all over the place. switching to the electric pump Allowed me to run all both the supply and return line on top of the frame rail on the passenger side, instead of inside the rail. And the wiring consists of 3 wires with a relay. All hidden in a new wire loom. I only start the car maybe a dozen times a year, So having the electric pump would also keep me from having to crank and crank and crank just to prime the fuel system to get it to fire up and get the mechanical pump to start really working. Now I'll just have to turn the key on for a couple seconds.

The carb is now a Holley 650, which doesn't make much difference, The regulator I heard was a great idea for extending the life of the pump, so I have already installed it.

Appears to be installed in the correct direction (first thing I checked, and had to several times just to make sure!). I mounted it about 1 foot away from the fuel tank, with the inlet to the pump facing upwards to allow gravity to help the fuel reach the pump.

Tell me about priming the pump... I have fuel immediately at the inlet. Is there a procedure for this? I figured with fuel flowing at the inlet, turning on the ignition would allow the pump to start pushing fuel.

Thank you for the formula, I can't imagine my application would require a huge amount of fuel. That guy with tech support might have been just trying to sell me a bigger more expensive pump!

Thank you!!!

 

If you want an electric pump, I suggest you go to a junk yard and get a tank from an '88-up EFI vehicle (could even be an earlier V6 EFI tank). Get a Walbro 255 pump to replace the factory unit. Add a return-type regulator.

You could just add an EFI pickup to your '85 tank, but the EFI tanks have baffles that the carb tanks don't.

In-tank pumps are superior to in-line external pump. No need to "prime" them, for instance. And, they are quieter.

 

A bypassing regulator can help extend FP life - not the cheap Holley dead-head regulator.

Good that you installed the electric FP correctly by the tank.

As far as priming the pump, you have fuel, so it's already primed.

 

Yes, but when the in-tank FP quits, you have to drop the tank.

 

Exactly the reason I prefer to avoid the in-tank pumps. I can handle replacing the external one once every year if I have to, that would be better than replacing the in-tank one once every 5-8 years.

It was also suggested to me, to look into the Carter P4070. The only thing I see that concerns me, is the inlet/outlet size. 1/4"!!! Will 1/4 fittings even flow the amount of fuel they advertise?!?! I am told these Carter elecetric fuel pumps are a lot quieter than the summit brand or the edelbrock brand of pumps.

 

We're running the P4070 pump on my daughter's car in my sig.
Dead headed to the Q-jet (no regulator or return line). working great for 2 years so far.
Can't speak for its "quietness"; rubber mounted, but against the sheetmetal/rear seat bulkhead, so it's very noticeable.
If you're concerned about noise, in-tank is the way to go.

 

Put in a quality pump, and it'll last a lot, lot longer...

 

very true.
The least I've ever gotten out of an in-tank pump was 160k miles over an 8-year period. The replacement in my C1500 has been in there for 240k miles over 10 years.

 

That is impressive!! I certainly haven't been that lucky. More than half the time I find a fuel pump not operating, I find a bad ground. Seems a lot of people are quick to condemn the pumps!!

 

I use the old Purolator version of that electric FP as a pusher to my stock block-mounted mechanical. But when the car gets back on the road, it will have the Carter M6626 still fed by the electric in "high demand" situations.