Fuel puddling, AFB 750, primaries siphoning?

[fshd4it]

After a long break, I'm back on tuning my Duster. Figure it's getting too much fuel (stock carb settings), and when I pulled the carb this morning there was gas laying in the bottom of the Air Gap on the driver's side. 360, Holley blue pump set at 5.5 psi (according to both gauges I've used); Carter 750, floats set at 7/16 & 15/16, New needle/seat assemblies. Pulled the top, zero junk in the bowls. I had this problem before with this carb, ended up being the secondary booster gaskets. Primaries were wet this morning (could have been from when I removed the carb though), any other things to look for before I replace the gaskets and reassemble?

 

[GTX JOHN]

Recheck Float Height.

 

[fshd4it]

Recheck Float Height.

Just checked them, they were right at 7/16". Thoughts on dropping them a bit? Say 1/16", or more?

 

[GTX JOHN]

That is already pretty low fuel level as I use as little
9/32.

I wonder if needles and seats are damaged. Never
bend floats against the needle and seats. Use a needle nose
to bend arms.

Invert the carb and blow thru the fuel inlet and see of hte seats
leak.

 

[Inertia]

Clear the air bleeds .

 

[Oldmanmopar]

The problem usually is the ethanol fuel. You need to put a return on the line after the mechanical fuel pump and before the carb . Due to the pressure dead ending up against the needle and seat. it pushes past when shut down.

The float does not have enough pressure to stop the fuel with ethanol fuel. And all fuel has it in now . They started using these filters on the carbureted cars in the late 70's due to the fuel at that time and it got worse since.

Many carbureted cars have a hard time restarting after warmed up and shut off because they flood from fuel bleeding past.

Electric pump carbureted cars are worse . On those systems you need to run a bypass pressure regulator. The old school pressure regulators don't work you need a bypass regulator. The the old school regulators still dead end the fuel pressure at the needle and seat. It needs to by-pass

Every car done here gets a return. The difference in performance is unbelievable. Get one and install it using the vent line for a 71-76 if you have a manual pump.

Electric pump carbureted cars get expensive. It was an extra $200 just for the braided line and fittings the regulator is around $80

Holley 12-881 Holley Carburetor Bypass Style Fuel Pressure Regulators | Summit Racing

Your welcome. Steve

 

[fshd4it]

I've hardly driven this thing, so it only gets ethanol-free 91 from a jerry jug. But I am planning on a bypass regulator, just haven't gotten there yet.

 

[Newbomb Turk]

I've hardly driven this thing, so it only gets ethanol-free 91 from a jerry jug. But I am planning on a bypass regulator, just haven't gotten there yet.

Fortunately you have a cold air intake. That helps a bunch but those carbs still boil off fuel at an alarming rate because the fuel bowls have no air circulating around them.

It’s a PITA for sure.

I’m all for a bypass. On pump gas street/strip cars it’s almost mandatory any more.

Part of it is alcohol in the fuel, but this fuel we get today is formulated for EFI so it’s blended for that and it plays hell with carbs.

 

[Professor Fate]

If you go for the fuel filter with a vapor return fitting, make absolutely sure the return nipple has a restrictor orifice in it, it's about 1/16". Some of the filters coming through now have been cheaping out and not making them with the restrictor in them. I've run into this issue with both Wix and Fram filters for sure so far- some have them, and some do not. Might be an old stock/new stock thing.
If you use one of the new ones, you can easily run into the situation where a standard pump can't supply enough fuel to the carb when most of the fuel is getting bled off through a wide-open 1/4" line. When I ran into this situation (after a lot of frustrated head-scratching) I ended up putting a 1/16 restrictor in the return line, and the problem was solved. Now I don't have to worry if the new filters have the required orifice or not.

 

[fshd4it]

If you go for the fuel filter with a vapor return fitting, make absolutely sure the return nipple has a restrictor orifice in it, it's about 1/16". Some of the filters coming through now have been cheaping out and not making them with the restrictor in them. I've run into this issue with both Wix and Fram filters for sure so far- some have them, and some do not. Might be an old stock/new stock thing.
If you use one of the new ones, you can easily run into the situation where a standard pump can't supply enough fuel to the carb when most of the fuel is getting bled off through a wide-open 1/4" line. When I ran into this situation (after a lot of frustrated head-scratching) I ended up putting a 1/16 restrictor in the return line, and the problem was solved. Now I don't have to worry if the new filters have the required orifice or not.

I was planning on running a return-type regulator. There's a cheap Holley dead-head unit on there now, I just need to decide which one to buy, and where to plumb the line into the tank. I welded a sump to the stock tank, so there's an extra port on that... or I could pull the sending unit (which actually works) and put a 3/8" nipple or bulkhead fitting in that.

 

[fshd4it]

Clear the air bleeds .

Sorry, scrolled right over that. Just the ones in the boosters, or into the body as well?

 

[Newbomb Turk]

I was planning on running a return-type regulator. There's a cheap Holley dead-head unit on there now, I just need to decide which one to buy, and where to plumb the line into the tank. I welded a sump to the stock tank, so there's an extra port on that... or I could pull the sending unit (which actually works) and put a 3/8" nipple or bulkhead fitting in that.

I wouldn’t put the fuel back in the tank through the sump. I out my return line fitting in the upper corner, passenger side of the tank.

The area of your vent should be at least the area of the feed line from the pump to the regulator and one size bigger is better.

As the fuel is returning to the tank it generates an incredible amount of vapors and they need a place to go.

 

[fshd4it]

My thought about returning to the sump, although the simplest way, would be the back pressure on the return line, having to push up through the fuel in the tank. Installing a bulkhead fitting up high on the tank (while still in the car) is obviously a no-go. That's why I was considering the sending unit plate. Easy to do on the bench, as I don't need the pickup tube any more.
This car came with a fuel cell in the trunk. I replaced the trunk floor, and installed a factory tank. The vent system still needs attention however. Might have to pull it back out and address both penetrations at the same time. PITA, though.

 

[RustyRatRod]

Search the net for "Edelbrock 1407 problems" and get ready to hold on. I had one and I could do nothing with it. Loading up, flooding and on and on and on. I got everything dead right by the book more than several times and never could get it right.

 

[fshd4it]

I have a 1406 on the shelf (probably needs a kit), maybe I'll go through that and see how that does for the time being. I'm in the middle of reading threads on here about it right now... The car came with a 700 dp, which may end up back on there eventually. I'm just more familiar with AFBs is all.

 

[fshd4it]

Buddy of mine dropped off a spare carb this afternoon, and of course it's a 1407. Maybe that's why it's a spare?

 

[Bewy]

You do not need a reg. These carbs will withstand 10 psi. Edel used a 7/16" float setting but not aware of any Carter AFB/AVS using that setting. The Comp Series AFB #4XXX used a 5/16" float setting. The 9000 series AFBs [ #9XXX ] used a 9/32" float setting.

 

[bee1971]

Carter Federal Mogul AFB 9755S Competition Series

Was brand new in the box before I bolted it on a few years ago doing some testing

Replaced the factory spring loaded .101 needles seats with Carter .110 needles and seats

Set floats at 3/8” drop at 1.25”

Pulled the primary boosters and drilled the idle feed tubes at .037”

Right now replaced the factory primary jets and installed .107 - Secondary .107

Pink springs for factory metering rods

Fuel pressure 6 psi mechanical pump

Carb works , very well indeed - Zero issues - Fine tuning jetting for cruise

 

[RustyRatRod]

You do not need a reg. These carbs will withstand 10 psi. Edel used a 7/16" float setting but not aware of any Carter AFB/AVS using that setting. The Comp Series AFB #4XXX used a 5/16" float setting. The 9000 series AFBs [ #9XXX ] used a 9/32" float setting.

View attachment 1716453516

With all due respect, I've never seen it and I've messed with a lot of Edelbrocks. All the ones I've ever dealt with lifted the needles off the seats and started flooding around 7 PSI and most times a little before. I'd understand if it was just one application and one carburetor, but it's over a long period with many different vehicles. We've obviously had differing experiences.

 

[Bewy]

RRR,
The Edel fuel inlet system is the same as the the the Carter AFB carbs that have the 5" air horn. The floats, needle & seats are interchangeable. There was need for Edel to change a system that had worked perfectly for decades. An Edel AFB air horn will fit a Carter AFB body & vice versa. The screw heads might be different.....

 

[Bewy]

I should have added:
Edel made off road spring loaded n/seats for offroad use. They may well flood with too high fuel pressure. I would never use them..

 

[LO23M8B]

Very first thing to do is put an insulated 1/2 inch gasket on it. Will lower the carb. temp a lot. I fixed this problem on a lot of cars just doing this. If it doesn't work, get a kit to check alcohol content in the fuel. Just because it says alco free it doesn't mean a thing.