c3corvette77

question for you all about the stock fuel pump. my 77 has a relatively strong 355, say 400 HP. the guy that built it for whatever reason put an edelbrock victor race fuel pump on it and a bypass. plumbed out of the pump, into the bypass, 1 outlet goes to the carb and the bypass fuel goes to the stock return line. to say i hate this arrangement is an understatement, i cannot get the fuel pressure to dial in even remotely right. now, what is the capacity of the stock 3 port fuel pump? will it feed 6-7 psi, no regulator and run a say 400 hp engine at 6500 RPM?

HamadUP

my stock GM fuel pump is pushing fuel at a constant 7 PSI @ idle.

c3corvette77

the big block and small block pumps are different. will the stock small block pump feed my motor well enough?

damoroso

Actually the big block and small block pumps are the same physically. You can get different pressures and volumes, but they'll bolt up and run fine. What makes you think you've got a fuel pressure issue?

c3corvette77

the car has a fuel pressure guage going into the carb that swings wildly between 2 and 12 psi. I swapped the guage and get the same thing. At rpm I see 9 to 11 psi. I have no fuel running out anywhere but at 11 psi there's no way the needles and seats are working like they should...

BKbroiler

I use a stock fuel pump on my 383, with the return line, probably around 350 hp, with no problems.

damoroso

You're right, the needle and seat won't work right (for long anyway) at those pressures. Sounds like a regulator issue more than anything. For what it's worth, I went with a straight pump (no bypass) regulator and guage. I'm running 4.5psi with no issues.

Rebelrob

Do you have a fuel filter? Might want to check that. damoroso is correct, you might need a regulator. I have a Holley Pump and regulator. I have it set at 6 psi according to my gauge. You want between 4-7 psi depending on your set up. 7 is really on the high side. Do you have any gas squirting out of the vent tubes on the carb?

c3corvette77

Fuel filter is good. I have a bypass as opposed to a dead head regulator. No fuel flowing out the vents. What size lines are your running pump to regulator and then back to the return? Does your fuel pressure guage swing all over or is it pretty steady?

larrywalk

1. The Edelbrock Race Fuel Pump requires a regulator - are you using one?

2. Unless you are using a liquid-damped fuel pressure gauge through a restrictor, you will see needle noise reacting to pressure pulses at the needles resonant frequency - in other words, don't worry about the peak readings.

3. Bypass return fuel: It's a good idea - in fact I added a bypass (through a .058" restrictor hole) to my Edelbrock Performer RPM Street Fuel Pump (Pn 1721) on my '78. The pump doesn't require a regulator and has three sets of fuel valves internally to provide good flow - much better than the one set in the stock pump.

If you're concerned about the bypass, a stock pump has an internal metering orifice of .058" diameter which lets a small amount of fuel return to the tank to avoid shutdown fuel expansion issues, and it also helps keep fuel cooler when running by keeping fuel in the line to the pump in constant circulation.

Unless you're capable of running faster than 12.0 in the 1/4, the stock pump with a return bypass will work fine.

damoroso

All good information, however, #2, I wouldn't use a liquid damped guage if it's under a hood. As the underhood temp increases, the viscosity of the liquid does too, changing the reading of the guage. I ran one, and it was showing zero fuel pressure after running for a while. Couldn't understand why, I called Summit thinking the guage was wrong and they told me not to run a liquid damped guage if you have closed engine compartment. Went to a dry guage, no more problem.

c3corvette77

i'm running a dry guage. the bypass is a barry grant, has an inlet from the pump, outlet to the carb and a return port for excess, this goes to the stock return line. i just can't get the pressure down where it's supposed to be. it's all over the place and very frustrating....

Rebelrob

I am not using my return line. But I plan to, just have not checked that off the list.
I am running 8AN line from the pump to reg to the carb. My gauge stays steady at 5.9-6.0. After I shut the engine down its still shows pressure until a few hours later it bleeds off.
It is not a liquid filled gauge as damoroso, describes. How does your car run?
Maybe try a new pump from the auto part store.

c3corvette77

car runs well, fast and strong. i'm thinking of either a stock pump or a performer street pump.

damoroso

Pressure regulators are for specific pressure ranges. Is it possible your regulator isn't correct for the pressures you want to run? This is the fuel pump and regulator I'm running. I can adjust the pressure easily and it stays consistent when running. And just like Rob, after shut down pressure stays for a bit then bleeds off. I know alot of guys like to run the return line, but I've had no issues without it. Might be something to consider. You might also give Holley tech line a call, they might be able to help.

http://www.summitracing.com/parts/EDL-1712/

http://www.summitracing.com/parts/HLY-12-803/

c3corvette77

Does it matter if the diaphragm bypass, which I have, is mounted before or after the carb? Mine is currently before the carb but all the diagrams I found show the bypass after the carb. Could this be the cause of my problem?

damoroso

I'm not sure at all, sorry. Like I said, give the Holley tech line a call. I'd bet within 10 minutes, you'd have the answer. Now I'm curious too!!

c3corvette77

Well, I emailed Barry Grant tech Monday. Told the exactly what I had, edelbrock victor pump, BG bypass, holley carb. Here it is Thursday and I have response zero. Maybe because I'm not running all Barry Grant they don't respond. Check with Holley next....

jimboscarbs

If you run the car hard the stock pump will not keep up
The Edelbrock units if I am not mistaken have an internal bypass spring that you can change based on needs one for alcohol and the other for gas the differnet spring rated come in the rebuild kits you need 5-7 psi at all times stock pumps wont flow enough volume

c3corvette77

The victor fuel pump, which I have, puts out 10 psi. Needs a regulator. The guy that built my car installed a Barry Grant diaphragm bypass before the carb. A bypass allows for use of the return system in the car. My biggest question is does the bypass have to be installed after the carb or can it be in line between the pump and the carb like a dead head regulator? It is currently in line between the pump and the carb. There are 3 ports, IN, RET and P/O. If you look at the diagrams the pump goes directly to the carb and the bypass is after the carb. The IN port is hooked to a fuel log, RET goes to the P/O port goes to a guage. The way its in the car the pump goes to the IN on the bypass, the P/O port feeds the carb and the RET is plumbed to the stock return to the tank.