Return fuel pressure regulator

[Cleve]

I am still thinking about the pressure regulator for the carburetor . There is a small quarter inch tube on the tank that is sealed off with a rubber cover. This tube is directly beside the main fuel suction tube for the engine. If I get a pressure regulator with a fuel return,, can I use that quarter inch tube to return the fuel to the tank from the pressure regulator? I don't want to drill a hole in the tank. If I can use this 1/4 in. tube as my return what pressure regulator would be recommended?
Thanks Cleve

[rich grsc]

Yes, that should be fine

[Cobraman]

Are you using a in tank fuel pump or mechanical. The reason I say this is I put a return line in with my setup but the fuel pump still produced to much pressure because of the resection of that 1/4 return I was unable to get pressure below15psi. Even with an6 fuel lines. I ended up inlargeing the return to 3/8 it can be done very carefully with the pump out of the tank. You can drill the 1/4 out to accept the 3/8 line then I used some fuel rated epoxy to install it has worked flawless now my fuel pressure is between 5 and 9psi which is what is needed. Hopefully this helps.

[Cleve]

Thanks for the comeback. I have a mechanical fuel pump on the engine, do you think that that would make a difference? My pump is on the engine, not in the tank. Its rated 5-8 psi. This should work.
Cleve.

[BUDFIVE]

Edit, answered earlier question. Typed while you were typing post #4. Mechanical pumps designed for carbs are totally different. Below is for in tank.

Yes with an in-tank fuel pump and a carburetor (usually 5-7 psi), the return line from a bypass regulator should be the same size as the feed. With EFI, the pressure is higher (usually 45-60psi) and this is less of an issue. This is because the pump produces flow (255lph for example). Pressure is created by the regulator holding back flow until the set point pressure is reached. The key point in a bypass system is except at wide open throttle MOST of the flow goes down the return line back to the tank. If the return line is small (1/4”), it restricts the flow, back pressure increases to the carb above the regulator set point. Pro-M racing has a great video on this.

Bottom line-I use 3/8” (6AN) feed and return lines, a 255LPH pump in the tank, and a bypass (return style) regulator like Holley 12-887 for carb or 12-886 for EFI. One benefit is later converting from Carb to EFI (or vice versa) is just a regulator swap. I just wrote about this in my build thread. cheers

[Cleve]

Thanks for the info. My mechanical fuel pump is on the engine, not in the tank and is rated for 5-8 psi. Hopefully this will work with a 1/4 in. fuel line return.

[rich grsc]

Wait, I based my answer on thinking you were going to an electric pump. There is NO return line on a mechanical fuel pump. You obviously have no idea on what you are wanting to do, zero reason for a return line.

[Jim1855]

A bypass (return) regulator for a carb and mechanical pump is a great combination. Some mechanical pumps need a regulator. I think a bypass style provides benefits.

Solves many fuel pressure problems such as overpressure due to vapor lock (percolation) caused by ambient or engine heat. I've watched fuel flow past the needles when the pressure gauge read 12psi from heat. Alcohol in fuel reduces the boiling point, then heat and/or altitude accentuate the boiling problems.

As Budfive mentioned the return line can/will restrict the return flow. If so the pressure at the carb will rise.

Cleve, many opinions have been expressed here. You get to make your own decision.

Jim

[rich grsc]

You don't get vapor lock on an engine running at idle.

OK, I went back and reread your posts. You have never answered where your fuel filter is located. Also you said you have a rubber fuel line running to the front of the car. The fuel line should be metal, so there is a HIGH probability that the rubber line could be collapsing, starving the engine of fuel. You have repeated said it slowly dies then won't restart for some time, sure sounds like a collapsed line starving the carb of fuel