Curious on when one of these is needed? I understand fuel injected cars need them but what about carbed cars? Is it needed?

I believe I have an issue with pressure being in the lines after the engine is shut off (as evident on an Autometer cowl mounted pressure gauge) causing fuel to pressurize in the bowls and then leak from the boosters on my Holley when the engine is not running...is this possible?

Are the needle and seat assemblies in the carb any good. They should be able to hold back the pressure in the line with the engine off. I'm thinking there is more line pressure when the pump is running than when it's off. If it can't hold back static pressure it's probably not doing a good job at full pressure.

No return line here. Comp140 and their deadhead regulator, mine doesnt maintain pressure when the engine is shut off, it bleeds off fairly quick.

A return regulator is better but dead heads do work. Here's a Detailed Link (http://www.centuryperformance.com/fuel.asp). I'm running a Mallory 140 and 5-port Aeromotive regulator. 1/2" feed and return lines.

Are the needle and seat assemblies in the carb any good. They should be able to hold back the pressure in the line with the engine off. I'm thinking there is more line pressure when the pump is running than when it's off. If it can't hold back static pressure it's probably not doing a good job at full pressure.

I'm thinking they're ok, I've never really had an issue with the needle or float other than when trash gets in there...but I've cleaned it all out time and time again, seems like after the engine has been ran for a prolonged period of time fuel will drip from the boosters and cause the engine to run rich at idle and hard to restart because the plenum is full of fuel.

A Holley tech mentioned something about the pressure in the lines.

No return line here. Comp140 and their deadhead regulator, mine doesnt maintain pressure when the engine is shut off, it bleeds off fairly quick.

Mine is slow to bleed off.

Curious on when one of these is needed? I understand fuel injected cars need them but what about carbed cars? Is it needed?

I believe I have an issue with pressure being in the lines after the engine is shut off (as evident on an Autometer cowl mounted pressure gauge) causing fuel to pressurize in the bowls and then leak from the boosters on my Holley when the engine is not running...is this possible?

Two things come to mind.if your needle and seat can not hold back residual fuel pressure..then by all means the float bowl level will rise and dump thru the boosters.Assuming that the needle valve does seat and hold..it would point towards pressure in the bowls.The bowl vents eliminate this.Have you tied the 2 vent stacks together to eliminate fuel slosh without introducing the top of the transfer tube to atmospheric pressure??Just a thought for you to consider.

Hey Dawg

I don't run a return line on my carbed 454, and guess what ? The garage stinks of gas after I run it. I put a plastic butter tub and plastic bag over the carb, but it still stinks. I don't know if it's the answer, but I'd run a back line if it would help reduce the gas smell. My buddies smoke in the garage, cause I don't let 'em light up in the house.

Two things come to mind.if your needle and seat can not hold back residual fuel pressure..then by all means the float bowl level will rise and dump thru the boosters.Assuming that the needle valve does seat and hold..it would point towards pressure in the bowls.The bowl vents eliminate this.Have you tied the 2 vent stacks together to eliminate fuel slosh without introducing the top of the transfer tube to atmospheric pressure??Just a thought for you to consider.

Havent tried this, how can I do this?

How much fuel psi do you run to the carb. About 9 - 9.5 psi the pressure will overcome the needle and seat assemblies and push them open causing uncontroled fuel bowl levels. Had this problem myself in the past. I now run -8 from mallory 140gph pump to a Jegs bypass fuel regulator with -8 back to the fuel cell. Run 7 psi fuel pressure. It bleeds off pressure very quickly after pump / engine is shut down. Also better suited to a nitrous addition later on.

Are the needle and seat assemblies in the carb any good. They should be able to hold back the pressure in the line with the engine off. I'm thinking there is more line pressure when the pump is running than when it's off. If it can't hold back static pressure it's probably not doing a good job at full pressure.
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In some cases the pressure will go up when you shut the engine off due to heat soak & it can be substantial
Had this problem years ago in a street toy where it would flood on hot days after running it hard
The pressure would rise from about 7 to 15+ (it pegged the gauge)
Solved it with a very small "bypass" from the pressure to supply side of the pump.
The factory did the same basic thing with some Q Jet applications many years ago for the same reasons.

How much fuel psi do you run to the carb. About 9 - 9.5 psi the pressure will overcome the needle and seat assemblies and push them open causing uncontroled fuel bowl levels. Had this problem myself in the past. I now run -8 from mallory 140gph pump to a Jegs bypass fuel regulator with -8 back to the fuel cell. Run 7 psi fuel pressure. It bleeds off pressure very quickly after pump / engine is shut down. Also better suited to a nitrous addition later on.

9 PSI from pump to regulator and 5-6 PSI after regulator to carb