Question on mechanical fuel pumps

[spstan]

Pulled the two bowls on my Holley 4175. Held the floats up and blew through the fuel inlets on both bowls. Needle and seats seemed to seal tightly with no air leakage. So I'm thinking nothing wrong with the needle and seats (no grit preventing sealing). My engineer friend claims, however, you can only blow air at around 2psi. So if nothing wrong with needle and seat it must be fuel pump is putting out too much pressure.

Mechanical fuel pumps off the shelf (mine is Adelphi) are only supposed to put out 5-11 psi. Talked to mechanics and watched You Tube. About equally divided on whether mechanical fuel pumps should be required to have a pressure regulator. So I'm interested in what percentage of people on this site who have carbureted vehicles also run a fuel pressure regulator.

I'm looking at a Holley 12-803 cause I've heard the Mr. Gasket regulators leak. Can anyone recommend another fuel pressure regulator I can use that would put out around 4-9 psi? Thanks Paul

 

[Big_John]

Have you checked the fuel pressure? Before saying that's the problem, check it to see if it really is.

$16 at Harbor Fright and that's a combo pressure/vacuum gauge. You should have a vacuum gauge in your toolbox anyway.... and you'll need a pressure gauge to set the pressure regulator if you want go that way.

The more new parts you put in the mix, the harder it is to find the problem.

 

[CBODY67]

FWIW, I put a 4175 Holley on my daily-driver car (a GM F-body). I had NO issues with fuel pressure with the stock fuel pump (which also fits the Chevy 302/290 V-8s of the late 1960s). NO issues with the Holley 4160 that was on it before that. Stock fuel pressure is usually spec'd by Holley at 5-7psi for the mechanical pumps. These experiences spanned about 300K miles of driving in all climate conditions of the times.

I hope you used a tube to pressurize the float needle and seat!

CBODY67

 

[Toolmanmike]

It never hurts to check the fuel pressure. Holley carbs will stand more pressure than Edelbrock/Carter carbs do but it's always good to check. I have seen stock replacement pumps put out around 11# or so. That will blow fuel past most needles.

 

[spstan]

FWIW, I put a 4175 Holley on my daily-driver car (a GM F-body). I had NO issues with fuel pressure with the stock fuel pump (which also fits the Chevy 302/290 V-8s of the late 1960s). NO issues with the Holley 4160 that was on it before that. Stock fuel pressure is usually spec'd by Holley at 5-7psi for the mechanical pumps. These experiences spanned about 300K miles of driving in all climate conditions of the times.

I hope you used a tube to pressurize the float needle and seat!

CBODY67

CBO "don't understand "used a tube to pressurize". I put a tube on the fuel inlet and blew into it while I held the float up. Is that what you mean? Paul

 

[CBODY67]

Yes. Thanks.

 

[NitrousTuner1]

If your buying any reman over the counter pump.... NO No need for a regulator.
Majority of Holley needle/seats operate fine up to psi.
It's the poorly designed Carter/Weber needle/seat that has issue's with anything over 5.5psi as well as large pot holes
You haven't mentioned what the problem is that your even trying to fix....
Been tuning for a living for decades. Can tune a Holley based carb blindfolded at this point