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Carb overflow

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Shankles McBullnose

Carb overflow

I've noticed the past few trips a bit of stuttering coming from my 81 f150. (460 and Holley 600) the carb finally filled up and started spraying fuel so it's stranded at my job. I'm thinking before I pull the carb and check my floats that it's an over pressure issue first. Currently have a mechanical pump with no regulator and currently no return line to the tank. The outlet is there on the pump for it but the PO has it capped. My question is, if I add the return line, and assuming that is the issue, will the carb only take in the fuel it requires?

Im not 100% sure but I would think due to it's design it would send the access through that return through back pressure. But obviously I'm not a carb designer...just figured I'd try that first then get a regulator next then clear the floats

81 F150 460/C6 600 cfm Holley

Gary Lewis

Re: Carb overflow

Administrator

If it didn't do it for the last few months/years then I doubt it is too much pressure. The mechanical pumps usually only put out about 6 psi and the Holley's are usually fine with that.

I suspect you may have gotten some bad gas. I did that once with a Holley and it gooed up the needles so badly they wouldn't seal. It flooded and gas went everywhere.

I would pull the float bowls off, inspect and clean the needles as well as the bowls, and put them back on. Start it up and see if the problem is gone - at least for a little bit. If it is the gas the problem will probably come back, but if it is too much pressure the problem won't have gone away at all.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

Shankles McBullnose

Re: Carb overflow

Well, I have only had it for a month unfortunately so I don't know if it did it in the past. But I just swapped the tank, fuel lines, added a filter, everything is new.

I won't rule out the bad gas however, since I did add some of the old gas from the other tank. Thinking about it now...I added 20 gallons from a place I never, ever utilize. Before that I had ethanol free in there....hmmm it's starting to make sense now....

81 F150 460/C6 600 cfm Holley

Gary Lewis

Re: Carb overflow

Administrator

Yep, that can do it. I ran several bottles of fuel system cleaner and a couple of tanks of gas through my '69 Super Bee and none of that made a difference. Finally at a roadside park I pulled the carb apart and found goo on the needles. Wiped that off and put it back together and had no more problems.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Carb overflow

Administrator

In reply to this post by Shankles McBullnose

I have a 460 with mechanical fuel pump and haven't encountered this (in 35 years of ownership)
But I've always had the return line connected....

Is it extremely cold where you are?
Maybe just the seals/seats are hard, or the diaphragm is stiff?

I know your truck never came with that engine but I would try to incorporate the return line back to the sender bung.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Shankles McBullnose

Re: Carb overflow

In reply to this post by Gary Lewis

Pulled the carb and the needle in the bowl in question would stick when up, hence the overfill issue. Managed to clear it enough to drive it home. Waiting on rebuild kit before I give it the full clean up but I should probably replace both needles to be safe. Thanks for the help

81 F150 460/C6 600 cfm Holley

Gary Lewis

Re: Carb overflow

Administrator

It isn't the fault of the needles, but something on them. And that something came in the gas, so if you don't burn that gas out or replace it you are likely to have the same problem over again.

In my case several cans of fuel system cleaner didn't do the trick, and burning the gas out didn't either. It was a combo of fuel system cleaner, burning the fuel out and replacing it with good, and finally cleaning the carb that did the trick.

Gary, AKA "Gary fellow": Profile

86 1/2 Brutus

Re: Carb overflow

I would assume from what you are saying, it's probably bad gss. It has happened to me far to many times. You have a mechanical fuel pump, so I think you are good there unless this has been an on going problem. I'd clean out the carb, get some fresh gas and see how that goes.

Nick and George
1986 1/2 F150 XLT Lariat 4X2 300 Six - C6 - 3:08 in a 8.8 - Fully Loaded - 8 Foot Box
Owned since new