Carburetor leaking fuel!!!

[SBSerpent]

Went out to fire up the Cobra and it just wouldn't stop idling very rough. Pulled the air cleaner and noticed fuel leaking down along the linkage that goes to the vacuum secondaries (Pencil in the photo shows where it is dripping from). Tried to re-start but now is flooded. Noticed that after the re-start attempt that fuel was flowing down into the secondary chambers but eventually stopped. Fuel was flowing in through the boosters. Any ideas as to what is going on? Stuck needle in the fuel bowl?

[TLHanna]

Stuck needle maybe?

[SBSerpent]

Also, when I removed the sight plug from the secondary bowl, fuel poured out.

[patrickt]

Just change out the needle and seat and reset your float levels. They only last about 7 to 10 years, if that. Now, you can't rely on the instructions from 50 years ago on setting floats. Gas percolates easier now and your carb probably doesn't sit level in your car. Put the float level as high as it will go, but below the sight hole, so that when you shut the car off hot, you do not see gas percolating in through the boosters and fuming up.

[patrickt]

On second thought, pull the bowls off and inspect what it looks like in there and see if you have gobs of white crap peeling off the metering block. If so, replace it. If you have something that's making your needle/seat stick open, you have to at least look for what it might be. A stuck N/S can be a potential fire hazard. In my gallery I have pics of some of my metering blocks that the ethanol gas just ate to pieces, while other blocks seemed immune to ethanol.

[patrickt]

Here, this is what I'm talking about:

[SBSerpent]

I pulled the bowl off to inspect. The float looks fine and does not have a hole in it because I can shake it and hear no fluid inside. I submersed it in water and saw no bubbles. I then submersed the entire bowl assembly with float and needle into a glass bowl of water and the float closed the needle and stopped rising right where it should according to the sight glass. I blew into the fuel inlet with the needle open and then turned the bowl upside down so that the float closed the needle. Free flow of air with it open; no flow of air with it closed. The rubber conical stopper at the top of the needle looks fine.

Dunno, maybe by removing the bowl I dislodged whatever was keeping the needle open. Gonna re-assemble and see what happens. First need to get a new bowl gasket.

If I want to replace the needle/seat assembly, how do I figure out which one I need? Summit racing has tons on their website. Search by using the Holley part number?

[novasscnc]

Also check the float bowls loosen up over time

[FredG]

I used the Summit kit last year. It will do just fine. Install a fuel line pressure gauge. Holleys can be temperamental if the fuel pressure is not within recommended specs.

Fred

[patrickt]

Originally Posted by FredG

I used the Summit kit last year. It will do just fine. Install a fuel line pressure gauge. Holleys can be temperamental if the fuel pressure is not within recommended specs.

Fred

I have an in-line, liquid filled, fuel pressure gauge right there at the feed to the Holley. You have to learn how it is affected by the temperature change under the hood to really appreciate it. The first time you see it reading zero psi and your engine is running like a champ is the first lesson....

[Gaz64]

Originally Posted by patrickt

I have an in-line, liquid filled, fuel pressure gauge right there at the feed to the Holley. You have to learn how it is affected by the temperature change under the hood to really appreciate it. The first time you see it reading zero psi and your engine is running like a champ is the first lesson....

Yes, a liquid filled gauge will do this because the gauge is sealed, and the internal pressure varies with temperature.
The small amount of air is a cushion at normal atmospheric pressure. The gauge internals are referenced to this.
Raise the internal temperature and pressure, and then the gauge will read correspondingly lower.

Adjusting fuel pressure should be performed with a cold engine, at about 20 degrees C.

I have had better success with non-liquid filled fuel pressure gauges.

[SBSerpent]

Originally Posted by SBSerpent

Went out to fire up the Cobra and it just wouldn't stop idling very rough. Pulled the air cleaner and noticed fuel leaking down along the linkage that goes to the vacuum secondaries (Pencil in the photo shows where it is dripping from). Tried to re-start but now is flooded. Noticed that after the re-start attempt that fuel was flowing down into the secondary chambers but eventually stopped. Fuel was flowing in through the boosters. Any ideas as to what is going on? Stuck needle in the fuel bowl?

Also, referring to my original photo, the union between the red anodized fuel line fitting that screws into the bowl and the blue coupling are a compression style union, correct? As such, there is no gasket at this union, correct? Just want to confirm.

[patrickt]

Originally Posted by SBSerpent

Also, referring to my original photo, the union between the red anodized fuel line fitting that screws into the bowl and the blue coupling are a compression style union, correct? As such, there is no gasket at this union, correct? Just want to confirm.

There is indeed a gasket between the fuel bowl and the inlet fitting. It should be in your kit.

[patrickt]

There may also be a spring and a Moraine brass filter in there as well. If they are, note the direction that it all goes in (or Google it), so that you put them back in correctly after cleaning them. I know they're in mine, so they might be in yours as well.

[patrickt]

This is what they look like. And they're actually a little trickier to get seated properly than you might think. Some Holley's have a teeny weeny little lip over on the inside of where the gasket seats and if you don't get down there and look the gasket sits on top of it funny and you get a drip.

https://www.summitracing.com/parts/h...SABEgKVnPD_BwE

[SBSerpent]

Originally Posted by patrickt

This is what they look like. And they're actually a little trickier to get seated properly than you might think. Some Holley's have a teeny weeny little lip over on the inside of where the gasket seats and if you don't get down there and look the gasket sits on top of it funny and you get a drip.

https://www.summitracing.com/parts/h...SABEgKVnPD_BwE

No brass filter and no lip on the fuel bowl inlet. Any specific torque on the 4 fuel bowl bolts? Or, is it a 'common sense & feel' torque value? I assume after a couple of engine cycles I will need to re-check the tightness on the bolts?

[TLHanna]

There are no gaskets used with AN type hoses and fittings unless the conical end of the fitting is damaged, then there is a soft washer type piece that can be used to help seal the fitting.

[TimG427]

The needle and seat stuck on my Cobra right after our Austin get-together last weekend. Pulled it out and cleaned it off and it's fine now.

[SBSerpent]

Originally Posted by TimG427

The needle and seat stuck on my Cobra right after our Austin get-together last weekend. Pulled it out and cleaned it off and it's fine now.

I gave mine a thorough cleaning as well and it moves smoothly but I still have a concern over the O-ring on the N&S assembly. I'm just gonna replace it entirely with a new one from the rebuild kit.

How did you realize your N&S were stuck? Was the car stumbling really bad? Smell of gas? Was it pouring through the boosters into the chambers?

[patrickt]

Originally Posted by SBSerpent

How did you realize your N&S were stuck? Was the car stumbling really bad? Smell of gas? Was it pouring through the boosters into the chambers?

Remember that any time fuel comes out of the boosters, when the butterflies are closed because you are idling, it will pool on top of the butterflies and then seep out through the throttle shaft and drip down on to the intake manifold. If you had a nickel for every post where some guy wrote "why is gas leaking out the side of my carb?" you'd be a millionaire. If it is on the secondary side on a vac secondary carb, it usually comes out the shaft and drips down off the plunger for the vacuum canister. If you look down the top of the carb while it is idling and you see little pools of gas on top of your butterflies then it means either your needle and seat is leaking or your floats are too high or the gas you are using is really $hitty and is percolating up and out through the boosters. A couple of years ago I did a full rebuild of my carb and set the floats dry on my bench. When I fired her up I set the floats to just at the base of the sight glass for both primary and secondary. Then I took her around the block three or four times and pulled her back in to the driveway (not the garage) and popped the hood and removed the air filter. Gas was dribbling out both primaries and secondaries at a pretty decent pace. I immediately shut her down and the prettiest white cloud formed about one foot over my carb that you have ever seen. If I had had a Lucky Strike in my hand I could have made a wonderful YouTube vid with it. In order for me to set my floats perfectly, so that I get no percolating after I shut her down on a hot day, I have to set the gas level about an eighth of an inch below the sight hole and the way I do it is by setting it just below the hole, then drive her, if she percs then set it a little lower, then repeat until both primary and secondary are set as high as possible without percolating out when hot.