Bypass vs Deadhead fuel pressure regulator question.

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MileHighDart

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So cant decide if I want or need a return line in my new system.
Going to run new 3/8 hardline from my new 3/8" pickup in tank to engine bay, add a regulator and gauge.

Engine is a freshly rebuilt, basically stock 5.9, with airgap and eddy 1406, dougs headers. The electric pump I have is a carter rotary vane P4070 which I think is the 4-8 psi pump.

Was reading on another forum, some guy said you cant use a bypass regulator with that pump because it has a bypass built into the pump. Don't know if that's right or not.

Basically I want to get some parts ordered so I can get this done.
So wondering, can I use a bypass type regulator and plug the bypass, in case I want to add a return like later? Or should I just get a deadhead type, and worry about the return later if I have vapor lock issues or something.
 
With one inlet and one outlet, I cannot see how it has a built in bypass.
 
RustyRatRod said:
With one inlet and one outlet, I cannot see how it has a built in bypass.
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Agree. I ran a dead head system on a 600 h.p. sbc, then switched to a return because everyone said it was better, guess what, no improvement. If u set the deadhead system up right, it will work for a bunch of h.p. Get into hi rpm and bigger h.p., then return system may be the way to go.. The pump should be behind the tank and lower if possible for both systems , unless in tank.
 
MileHighDart said:
So cant decide if I want or need a return line in my new system.
Going to run new 3/8 hardline from my new 3/8" pickup in tank to engine bay, add a regulator and gauge.

Engine is a freshly rebuilt, basically stock 5.9, with airgap and eddy 1406, dougs headers. The electric pump I have is a carter rotary vane P4070 which I think is the 4-8 psi pump.

Was reading on another forum, some guy said you cant use a bypass regulator with that pump because it has a bypass built into the pump. Don't know if that's right or not.

Basically I want to get some parts ordered so I can get this done.
So wondering, can I use a bypass type regulator and plug the bypass, in case I want to add a return like later? Or should I just get a deadhead type, and worry about the return later if I have vapor lock issues or something.
Click to expand...


Unless you are going to 60 foot quicker than 1.40ish you don't need a return line.

Back in the early 1980's I used to block off the internal bypass in the Holley blue pumps and ran a number 8 high speed bypass valve back to the tank. The real is the weight of the fuel in the fuel line. A 3/8 line has more fuel by weight and volume as the same length of 5/16 line. A 1/2 has more weight and volume that the 3/8 line. As the line from the pump to the carb gets bigger, you have to overcome the weight of the fuel in the line, or it will stand off. Meaning you can have pressure on the gauge but no fuel moving in the line.

The only way to overcome that is by raising the line pressure. IIRC, those blue pumps were said to have a 15 pound spring in them. Of all I tested, most were actually 10-12 pounds. I would block the internal by pass and set the line pressure to 25 pounds.

The Holley engineers didn't like it, but it was easier on the pumps and stop fuel stand off in the line.
 
yellow rose said:
It's like an oil pump rusty, where the bypass valve opens and dumps the fuel back into the inlet side of the pump.
Click to expand...

Where it gets sucked right back into the pump? That's sorta not a bypass. lol
 
famous bob said:
Agree. I ran a dead head system on a 600 h.p. sbc, then switched to a return because everyone said it was better, guess what, no improvement. If u set the deadhead system up right, it will work for a bunch of h.p. Get into hi rpm and bigger h.p., then return system may be the way to go.. The pump should be behind the tank and lower if possible for both systems , unless in tank.
Click to expand...

Return systems are nice, but people have run deadheaded systems for decades with zero problems. As long as the right regulator is used, it really doesn't matter.
 
yellow rose said:
Unless you are going to 60 foot quicker than 1.40ish you don't need a return line.

Back in the early 1980's I used to block off the internal bypass in the Holley blue pumps and ran a number 8 high speed bypass valve back to the tank. The real is the weight of the fuel in the fuel line. A 3/8 line has more fuel by weight and volume as the same length of 5/16 line. A 1/2 has more weight and volume that the 3/8 line. As the line from the pump to the carb gets bigger, you have to overcome the weight of the fuel in the line, or it will stand off. Meaning you can have pressure on the gauge but no fuel moving in the line.

The only way to overcome that is by raising the line pressure. IIRC, those blue pumps were said to have a 15 pound spring in them. Of all I tested, most were actually 10-12 pounds. I would block the internal by pass and set the line pressure to 25 pounds.

The Holley engineers didn't like it, but it was easier on the pumps and stop fuel stand off in the line.
Click to expand...
I put a 15 pound holley spring in an 8 pound pump once, guess what happened. 15 pound pump !
 
is there any merit to running a return style system in order to keep fuel cool, considering the OP is in thin air and a hot climate ?
 
yellow rose said:
Unless you are going to 60 foot quicker than 1.40ish you don't need a return line.
Click to expand...

Well, I cannot agree THERE.

With ethanol laced gas, a good return system really helps. A LOT. In fact, I think a good return system might be more important on a street car.
 
If vapor lock is a consideration, getting rid of the Edelbrock carb is the first place to start. They have small float bowls that pick up alot of heat from the engine. I have a dead head system on my 64 Sport Fury using a Carter pump, and 1/2 inch line to the regulator. Then 3/8 line to each bowl. No issues.
 
furyus2 said:
If vapor lock is a consideration, getting rid of the Edelbrock carb is the first place to start. They have small float bowls that pick up alot of heat from the engine. I have a dead head system on my 64 Sport Fury using a Carter pump, and 1/2 inch line to the regulator. Then 3/8 line to each bowl. No issues.
Click to expand...
I have a 3310 Holley with a 1/2" phenolic spacer under it. Was using a Carter mechanical pump. Had the boiling fuel issue. Could not get rid of the problem in any conventional way. Finally after some very frustrating hot summers I went to a high-pressure in-tank Walbro electric pump, -6AN supply & return hoses, and a bypass regulator. No fuel problems of any kind since that work was done. Far as I'm concerned , the bypass regulator should always be used.
 
RustyRatRod said:
Well, I cannot agree THERE.

With ethanol laced gas, a good return system really helps. A LOT. In fact, I think a good return system might be more important on a street car.
Click to expand...


You are more correct than not. I actually looked at doing a return system on my DD. By the time I laid it out and looked where to put all the fittings I said piss on it.

I rebuilt my Carter mechanical pump, did a little internal turd buffing on it and called it good.
 
yellow rose said:
Unless you are going to 60 foot quicker than 1.40ish you don't need a return line.

Back in the early 1980's I used to block off the internal bypass in the Holley blue pumps and ran a number 8 high speed bypass valve back to the tank. The real is the weight of the fuel in the fuel line. A 3/8 line has more fuel by weight and volume as the same length of 5/16 line. A 1/2 has more weight and volume that the 3/8 line. As the line from the pump to the carb gets bigger, you have to overcome the weight of the fuel in the line, or it will stand off. Meaning you can have pressure on the gauge but no fuel moving in the line.

The only way to overcome that is by raising the line pressure. IIRC, those blue pumps were said to have a 15 pound spring in them. Of all I tested, most were actually 10-12 pounds. I would block the internal by pass and set the line pressure to 25 pounds.

The Holley engineers didn't like it, but it was easier on the pumps and stop fuel stand off in the line.
Click to expand...

Excellent post!
 
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