Carburetor Flooding

[eafree]

I started up my car yesterday and I had a few problems. The main question I have is: I have a Holley 600 cfm carburetor, that I rebuilt. I'm running a 97 GPH Free flow electric fuel pump that is preset at 7 psi. I'm running a 90 GPH @ 7 psi fuel filter. The problem I'm havig is that the carburetor is flooding out of the stand pipe(vent) on the carburetor. I did not replace the floats and have not had the chance to check to make sure that there not sinking. I will test the fuel pressure and check the floats in the next day or two. Any thoughts from the pros.

Eric

 

[one finger john]

I started up my car yesterday and I had a few problems. The main question I have is: I have a Holley 600 cfm carburetor, that I rebuilt. I'm running a 97 GPH Free flow electric fuel pump that is preset at 7 psi. I'm running a 90 GPH @ 7 psi fuel filter. The problem I'm havig is that the carburetor is flooding out of the stand pipe(vent) on the carburetor. I did not replace the floats and have not had the chance to check to make sure that there not sinking. I will test the fuel pressure and check the floats in the next day or two. Any thoughts from the pros.

Eric

Run a pressure regulator set at the recommended PSI. Just to be sure. Would be nice if pressure could be set as you run down the road, not at idle. Also, does this pump have a return line? Or as they say, is it "deadheaded"? IE no return line.

John

 

[eafree]

John, no return line line. I will try and check the pressure this evening maybe, we will have to see how the day goes.
Eric

 

[Mike]

Is it flooding from both vents, or only one?

Whose kit did you use for the rebuild? A Holley needle and seat should be OK with 7#'s. A parts store kit needle and seat may not.

Did you put a bit of oil on the needle and seat o-ring before threading it into the bowl? That will usually prevent any damage to the o-ring, as it passes through the machined area of the bowl. If it gets damaged, that can cause flooding over.

Pull the needle and seat from the bowl and make sure nothing is caught up in it. Give it a quick shot of carb cleaner to be sure.

Pop off the offending bowl and invert it. Verify you don't have a heavy float. (It's easy with a brass float, you can hear fuel inside it as you shake it.) Oil the needle and seat o-ring and reassemble. Measure from the ceiling of the bowl (which is now at the bottom, because you are inverted) to the top of the float (which is also at the bottom). Set the float level so you have about .375", which will get the top of the float pretty much parallel with the ceiling of the bowl. Anything less could cause you some issues.

Once you are sure everything is OK at that end, give it another try. If it still wants to flood over, then it's time to check your fuel pressure and regulate if necessary.

I cannot stress to people enough that everything must be checked. If you don't verify things, you are merely hoping the individual that did the assembly work was having a really good day. We installed a fuel pump from a very well-known carb/fuel systems manufacturer on a freshen job. Without naming any names (rhymes with Harry Gant), I can say this company had done nothing more than purchase a Carter fuel pump, drill and tap the inlet and outlet for 9/16-18 X #8 fittings. The customer took everything home and was back the next day, complaining his fuel pressure was too high and the carb was flooding over. He had the fuel pump in hand and as he laid it on the counter, I saw something fall out of a fuel fitting. It was a piece of metal, looking suspiciously like a drill shaving. I pulled another, brand-new pump from the shelf and pulled the bottom off. Like I said, this well-known manufacturer had merely drilled and tapped the pump. Without taking the pump apart, mind you! Not checking their work had caught us with our knickers around our knees. I had six pumps in stock, all of which were full of metal shavings.

Check everything twice, before you use it. And then check it again, before you actually go to bolt it on.

 

[Screaming Metal]

Mike and OneFingerJohn have ya taken care of! Darn, all these guys are good....this is a good place to be for roddin'! Also, set your regulator on the low side (about 3 to 4 psi) and start adjusting it up slowly. It should start fine, but if she stumbles and misses slightly, shut her down and raise her 1 psi at a time.
These carbs and kits, when you rebuild the carbs, your needle seat is angular, and it doesn't take alot of pressure to force fuel past it. A new seat that hasn't had enough time to mate to the set, is all the more susceptable to flooding, thats the reason for raising the pressure slowly.
On a street motor less than than 400 horses, try about5 psi. Once you find where the motor runs good, don't go over a 1/2 pound over that. If your into the 1/4 mile thing and your worried about starving the motor off the line....put on a fuel log...

 

[eafree]

Is it flooding from both vents, or only one?

Whose kit did you use for the rebuild? A Holley needle and seat should be OK with 7#'s. A parts store kit needle and seat may not.

Did you put a bit of oil on the needle and seat o-ring before threading it into the bowl? That will usually prevent any damage to the o-ring, as it passes through the machined area of the bowl. If it gets damaged, that can cause flooding over.

Pull the needle and seat from the bowl and make sure nothing is caught up in it. Give it a quick shot of carb cleaner to be sure.

Pop off the offending bowl and invert it. Verify you don't have a heavy float. (It's easy with a brass float, you can hear fuel inside it as you shake it.) Oil the needle and seat o-ring and reassemble. Measure from the ceiling of the bowl (which is now at the bottom, because you are inverted) to the top of the float (which is also at the bottom). Set the float level so you have about .375", which will get the top of the float pretty much parallel with the ceiling of the bowl. Anything less could cause you some issues.

Once you are sure everything is OK at that end, give it another try. If it still wants to flood over, then it's time to check your fuel pressure and regulate if necessary.

I cannot stress to people enough that everything must be checked. If you don't verify things, you are merely hoping the individual that did the assembly work was having a really good day. We installed a fuel pump from a very well-known carb/fuel systems manufacturer on a freshen job. Without naming any names (rhymes with Harry Gant), I can say this company had done nothing more than purchase a Carter fuel pump, drill and tap the inlet and outlet for 9/16-18 X #8 fittings. The customer took everything home and was back the next day, complaining his fuel pressure was too high and the carb was flooding over. He had the fuel pump in hand and as he laid it on the counter, I saw something fall out of a fuel fitting. It was a piece of metal, looking suspiciously like a drill shaving. I pulled another, brand-new pump from the shelf and pulled the bottom off. Like I said, this well-known manufacturer had merely drilled and tapped the pump. Without taking the pump apart, mind you! Not checking their work had caught us with our knickers around our knees. I had six pumps in stock, all of which were full of metal shavings.

Check everything twice, before you use it. And then check it again, before you actually go to bolt it on.

Mike, it is leaking only out of the front vent.
The kit was a holley kit.
I pulled the needle and seat and checked it and all was okay, so I swapped it with the needle and seat out of the aft bowl, no help.
I double checked float hieghts and they were good, also made sure I didn't have a heavy float.

I will have to check fuel pressure and regulate as needed in the next day or two.

Thanks for the info, it has been awhile since I had messed with a holley carb, I had looked at these items previous to the post. I just wanted to make sure that I was not missing anything, and I went back through it again.

Eric

 

[GMRodder]

Just for info purposes

The most common problem in new builds is attaching the fuel line to the carb without flushing the new fuel lines you just installed.
(Most professional builders preflush the lines before they install them on the vehicle.)
Always flush the lines or debris and grit in the lines will lodge in the needle and seat.
Be careful when flushing as it is easy to spill and catch fire with a new hi volume fuel pump, use a proper setup and container.
( I have a fuel can with a line fitted on to it and a line with a fitting that the carb fuel line can attach to it, thus no spillage can occur)
Disconnect the power to the coil, have a fire extinguisher handy, do in a well ventilated place and make sure you have help never do this alone.

Just my humble two cents worth. I have seen a dead wasp come out of a brand new 3/8" steel fuel line I bought at a parts store when I flushed it.