Sourcing 5-6 psi fuel pump help

[ahoke]

Fuel pump went out on my '72 C20 350 with the stock quadrajet. The one that was on it was a AC Delco mechanical pump with a 3/8 outlet fitting and a return line with the elongated pump body. Took a while but I found this one from summit:

https://www.summitracing.com/parts/CRT-M6101

Installed and the carb is flooding, rebuilt the carb, adjusted float, still floods. Looked on carter's website and says the psi min is 7.5 and max 9, not the 6 summit states. ANYWAY.....anyone have any advice on finding one with lower pressure rating? From what I can tell quadrajet likes about 5 or 6psi. I'd prefer not to have to add a pressure regulator inline if I can avoid it.

[53burb]

I haven't heard about quadrajets being sensitive to pressure....Edelbrocks I hear alot of....one of the cures they use, if they dont want to use a separate fuel regulator, is they use an Edelbrock fuel pump...they pump at a lower psi....

[Rust_never_sleeps]

Is there fuel flowing back to the tank through the return?

[jumpsoffrock]

I don't have particularly good news for you, but this issue is not anything new and is all over the internet.

The short of it is that the fix is to start running a pressure regulator.

I run a stock Holley 1-bl carb on my old ford truck for 10 years with no regulator--thousands of miles between 2011 and 2021. Pump installed in 2013 or so went bad and replaced with a new one, and for heavens sake I couldn't get the bowl to stop overflowing.

I paid $50 at autozone and got a simple regulator. Generally speaking it fixed my issue.


The talk on the internet is that the pressure regulation of most new pumps is very loose, with most pumps putting out 8-9, and some youtube people saying they've seen 11-15 from a stock mechanical pump meant for an application that calls for 3-5 psi. Not ideal....


Good luck.

[54blackhornet]

I had the DualJet rebuilt for my 71 C/20 307. It would not run properly until I installed a fuel regulator. I had an inexpensive Mr Gasket on my shelf, installed it and set it for five lbs. engine runs like a sewing machine now.

[1970cstblazer]

Originally Posted by ahoke

Fuel pump went out on my '72 C20 350 with the stock quadrajet. The one that was on it was a AC Delco mechanical pump with a 3/8 outlet fitting and a return line with the elongated pump body. Took a while but I found this one from summit:

https://www.summitracing.com/parts/CRT-M6101

Installed and the carb is flooding, rebuilt the carb, adjusted float, still floods. Looked on carter's website and says the psi min is 7.5 and max 9, not the 6 summit states. ANYWAY.....anyone have any advice on finding one with lower pressure rating? From what I can tell quadrajet likes about 5 or 6psi. I'd prefer not to have to add a pressure regulator inline if I can avoid it.

I hate Carter mechanical pumps. Never had any luck with them. I would get at minimum a Delphi brand or AC Delco brand replacement pump. I'm running a reman 1990 vintage AC pump on my Blazer. I don't use any fuel with ethanol in it, so it works well.

[twoskies]

Had a Rochester on mine from the Start, kept having issues with it, Carb not fuel pressure, pressure with Stock Fuel Pump was always 8 to 9
Bought an Edelbrock and hooked up Pressure Regulator
Not had an issue since

Besides, the Regulator looks Custom. lol

But i already bought an Edelbrock Fuel pump 6 PSI max, going to change it out this Winter, probably still run the regulator

[ahoke]

Appreciate all the knowledge and advice. Threw the mr. gasket dial regulator on just for simplicity's sake before committing to ordering a more quality option. Still having the flooding issue with the carb. I think the plan at this point is to swap the float in the carb out, switch the mechanical fuel pump with the return out for one without a return, and then install a regulator downstream with a return line.
When it comes to mechanical fuel pumps why are some flatter and others the cylinders are elongated like a soup can?

[1970cstblazer]

Seeing tons of utter failures right out of the box with recently produced pumps, I'd rather chance a NOS pump at this point!

Here is the correct one for your application:

1972 series 20 350 with Turbo Hydramatic:

6470569 or 40867

[raggedjim]

Keep an eye on the Mr. Gasket dial type regulators. Had one on my blazer and the gasket failed after a year or so. Very exciting episode.

It was in 2018 so maybe they have fixed the problem???

Good luck, Rg

[ahoke]

Originally Posted by 1970cstblazer

Seeing tons of utter failures right out of the box with recently produced pumps, I'd rather chance a NOS pump at this point!

Here is the correct one for your application:

1972 series 20 350 with Turbo Hydramatic:

6470569 or 40867

Would rather not reroute the lines in place, any idea what the model number for the outlet orientation that would be similar to the Carter one I got from summit would be?

[1970cstblazer]

Looks similar to me!

[ahoke]

One I pulled off in on the left and the one on the right is the 40867. Hard to see in pics but on the 40867 the inlet/return are pointed straight at the radiator/fan whereas the old one, they point towards the fender.

[54blackhornet]

I bought a pump from Napa for my 307. The threads for the input line were buggered up so bad that the inlet line would not engage into the pump. Returned it and found a nos Delco pump. Still working fine years later.

[Willshook]

At 40 GPH and even 9 PSI, I can't see how that's causing flooding. You don't need a fuel pressure regulator at that output.

What I typically find is that it's not the PSI - it's the GPH; "muscle car" pumps tend to put out 100+ GPH and that's just too much for stock carb to deadhead at. But that's not what's happening here.

I would check the needle and seat again to be sure there's not a piece of gunk there from when you changed the pump. I'm confident the problem isn't flow or pressure overwhelming the seat - it's that the seat isn't closing.

I've also seen a ton more failures in stock pumps out of the box any more; I only run Holley mechanical pumps any more for carbs. Rebuildable, too - and you can clock the outlets.