Holley Fuel Pressure
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Cargo Master
Joined: Jul 2010
Posts: 2,099
Likes: 8
From: York, Pa
Holley Fuel Pressure
I recently put a almost new Holley 600 on my 400. It for some reason would occasionally flood itself out of either bowl. Both bowls were set properly so that is not the issue. I swapped needles out of my other Holley 600 that were Quickfuel brand that I knew to be good. This weekend I had it do it again, this time is was the rear bowl.
Every time this has happened the rpms were higher and usually coasting letting the engine hold back. Today I rigged up my tools for fools vacuum that is supposed to be a fuel pressure gauge too. I didn't have a tee setup so I just ran it till the bowls went dry.
Both times I did it I had like 6.5-7 psi at idle and a steady 7ish revved up at what I would guess maybe 2500 since I have no tach.
This is the first Holley that I've had this issue with and can't believe I need a regulator. Has anyone else had the issue?
Every time this has happened the rpms were higher and usually coasting letting the engine hold back. Today I rigged up my tools for fools vacuum that is supposed to be a fuel pressure gauge too. I didn't have a tee setup so I just ran it till the bowls went dry.
Both times I did it I had like 6.5-7 psi at idle and a steady 7ish revved up at what I would guess maybe 2500 since I have no tach.
This is the first Holley that I've had this issue with and can't believe I need a regulator. Has anyone else had the issue?
Elder User
Joined: Feb 2011
Posts: 575
Likes: 6
From: Knoxville, TN
pressures fine. adjust fuel level in bowl by adjusting the float and try again. Fuel level should be right at the bottom of the fuel window on the side. lightly rock the truck and you should see it splash up on the window or pull the plug and see if it splashes out.....tons of info and videos on how to do it.....see if that helps your issue
Hotshot
Joined: Feb 2004
Posts: 10,867
Likes: 2,626
From: The Shenandoah Valley
Older Mopars had good volume FPs but typically, 3.5-4 psi. Your Ford at 7 psi is typical for 351M/400. Holleys work on both, but you do a bench setting dry just to get in the ball park ..... you have to use the sight window and adjust so the fuel is just starting to dribble out and no higher.
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Cargo Master
Joined: Jul 2010
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From: York, Pa
I do have the floats set that the fuel is slightly below the hole and takes a little rocking to get it to come out.
I was and still am tempted to use a set of older bowls or floats off one of my other parts carbs.
Like I said it works great while there is a demand for fuel. Only when I let the engine hold itself back with the throttle plates closed it likes to drown itself. Even with my known to work fine Quickfuel needle and seats it still does it.
I was and still am tempted to use a set of older bowls or floats off one of my other parts carbs.
Like I said it works great while there is a demand for fuel. Only when I let the engine hold itself back with the throttle plates closed it likes to drown itself. Even with my known to work fine Quickfuel needle and seats it still does it.
Fleet Mechanic
Joined: Jan 2014
Posts: 1,946
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Could it be that it's not overfilling but, simply, that the bowls are leaking. Or they could be leaking from around the bowl screw gaskets. You've got to verify where the fuel is coming out from. I had a brand new Holley once, that had a warped bowl and it leaked like crazy.
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Cargo Master
Joined: Jul 2010
Posts: 2,099
Likes: 8
From: York, Pa
Could it be that it's not overfilling but, simply, that the bowls are leaking. Or they could be leaking from around the bowl screw gaskets. You've got to verify where the fuel is coming out from. I had a brand new Holley once, that had a warped bowl and it leaked like crazy.
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Cargo Master
Joined: Jul 2010
Posts: 2,099
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From: York, Pa
That's probably what I'll do. I had thoughts of maybe a little dirt is getting in there somehow and getting embedded in the little black tip on the needle. My filter looks as clean and clear as it should be. I use a newer plastic tank and never get any junk in the filter.
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Cargo Master
Joined: Jul 2010
Posts: 2,099
Likes: 8
From: York, Pa
A little embarrassing update:
I was messing around with the carb this morning deciding if I wanted to switch bowls or not. I decided to pulled the rear needle and seat and again and have a look. This time I saw a almost microscopic piece of something black in the seat. I cleaned it and put it back in and runs good...for now.
So why and where did the black stuff come from when my filter is clean? I knew I had put new fuel line on from the front to back last summer but decided to check it out. It turns out I either forgot or just didn't do the short piece at the front from the frame to the pump. I'm almost certain the 20+ year old hose is degrading and it's too small for the cheap Mr. Gasket filter I probably shouldn't be using.
I had the hose thing happen on my highboy a few years ago. Once I switched it to ethanol compatible hose it stopped the problems that truck had.
I was messing around with the carb this morning deciding if I wanted to switch bowls or not. I decided to pulled the rear needle and seat and again and have a look. This time I saw a almost microscopic piece of something black in the seat. I cleaned it and put it back in and runs good...for now.
So why and where did the black stuff come from when my filter is clean? I knew I had put new fuel line on from the front to back last summer but decided to check it out. It turns out I either forgot or just didn't do the short piece at the front from the frame to the pump. I'm almost certain the 20+ year old hose is degrading and it's too small for the cheap Mr. Gasket filter I probably shouldn't be using.
I had the hose thing happen on my highboy a few years ago. Once I switched it to ethanol compatible hose it stopped the problems that truck had.
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Cargo Master
Joined: Jul 2010
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From: York, Pa
Ya no kiddin...I don't mind a little challenge but after a while it's gets old.
I wasn't planning on putting a fuel pump on it but still haven't ruled it out. Anyone have any thoughts to wether they degrade and contaminate like the hose with ethanol? My old 390 pump never seemed to cause a problem, it was very old and didn't seem to mind ethanol. I'm sure this one is equally as old but works fine. My 400 is pretty wore out so who knows how long it'll actually be in there. In other words my cheapness is kicking in.
I wasn't planning on putting a fuel pump on it but still haven't ruled it out. Anyone have any thoughts to wether they degrade and contaminate like the hose with ethanol? My old 390 pump never seemed to cause a problem, it was very old and didn't seem to mind ethanol. I'm sure this one is equally as old but works fine. My 400 is pretty wore out so who knows how long it'll actually be in there. In other words my cheapness is kicking in.
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Cargo Master
Joined: Jul 2010
Posts: 2,099
Likes: 8
From: York, Pa
The only issue I had was on my highboy the hose seemed to turn to dust. I could see it being caught in that filter, once I changed the hoses it stopped. I assumed it was from ethanol but maybe was just more age related.
Senior User
Joined: Aug 2002
Posts: 149
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From: Amarillo TX
I had one that had junk in the needle seat, it was brand new out of the box. Found that the thin gasket for the needle adjustment screw was coming apart. I cut a new one out of some good black gasket material and the problem went away. When I took the needle out the third time( the flow would not stop) the gasket just fell apart. Might check the needle O-ring and make sure it is is perfect shape also. O-rings are cheap but can cause a mind numbing problem.
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Cargo Master
Joined: Jul 2010
Posts: 2,099
Likes: 8
From: York, Pa
That's interesting but I believe I found my real problem. In addition to the old hose I said I forgot to change I think my fuel pump went or is going bad. After I had changed the hose I had it sitting their idling getting ready to take the dog for a ride I heard something strange. I was walking around the front when I heard a loud snap or pop like a popping a balloon. So I looked for leaks and doing nothing. On the test drive it spits and sputters in the secondaries but runs fine otherwise.
So I hook the fuel gauge back up and it hits 6 psi then settles to about 4-4.5. I'm not going to run it anymore till my new pump comes. I had to get a few other things so I made a rock auto order and found they had a Carter for $15.
I just can't believe what I heard was a fuel pump go bad but I have no idea what it could be. The fact that it did make 6.5-7 before makes the most sense.
So I hook the fuel gauge back up and it hits 6 psi then settles to about 4-4.5. I'm not going to run it anymore till my new pump comes. I had to get a few other things so I made a rock auto order and found they had a Carter for $15.
I just can't believe what I heard was a fuel pump go bad but I have no idea what it could be. The fact that it did make 6.5-7 before makes the most sense.