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  #1 (permalink)  
Old 08-09-2020, 02:01 PM
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Default Carburetor leaking fuel!!!

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?
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Last edited by SBSerpent; 08-09-2020 at 02:28 PM..
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Old 08-09-2020, 02:17 PM
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Stuck needle maybe?
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Old 08-09-2020, 02:32 PM
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Also, when I removed the sight plug from the secondary bowl, fuel poured out.
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Old 08-09-2020, 02:40 PM
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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.
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Old 08-09-2020, 02:46 PM
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Also check the float bowls loosen up over time
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Old 08-09-2020, 02:48 PM
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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.
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Old 08-09-2020, 03:04 PM
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Here, this is what I'm talking about:

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Old 08-09-2020, 04:06 PM
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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?
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Old 08-09-2020, 04:14 PM
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The rebuild kit will come with a couple of different N/S combinations. It will also have all your gaskets. On my Holley, two of the needle and seats looked like they were an exact match. One was .110 and the other was .097, but the instruction sheet that came with the kit indicated that the .110 was the correct match for a needle and seat marked with an H on it (which my needle and seat did). Here's a tip: Put a dab of Vaseline on the black O-ring; it makes the job way easier.
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Old 08-09-2020, 04:18 PM
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What fuel pressure do you run?

Can you see the seat size stamped at the top of near the flats?

Although your water test can give you a little idea, it doesn't compare, since fuel has a different density (lighter), the float is displaced at a different height.
Also fuel will creep past a bad needle, and past a bad o-ring.

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Old 08-09-2020, 05:43 PM
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Quote:
Originally Posted by patrickt View Post
The rebuild kit will come with a couple of different N/S combinations. It will also have all your gaskets. On my Holley, two of the needle and seats looked like they were an exact match. One was .110 and the other was .097, but the instruction sheet that came with the kit indicated that the .110 was the correct match for a needle and seat marked with an H on it (which my needle and seat did). Here's a tip: Put a dab of Vaseline on the black O-ring; it makes the job way easier.

Is there a specific rebuild kit that I need to order? Again, Summit Racing has lots of kits. My carburetor is a Holley Street Avenger series, p/n 0-83770.
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Old 08-09-2020, 05:55 PM
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I'd say it is a .110 needle and seat.

And this would be the whole kit you need:

https://www.holley.com/products/fuel.../parts/0-83770

Roll onto service parts, then down to 37-935:

https://www.holley.com/products/fuel...t/parts/37-935
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Old 08-09-2020, 06:06 PM
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Yeah, that looks pretty good. Summit will have it at your door by Wednesday,
https://www.summitracing.com/parts/h...5/applications
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Old 08-09-2020, 07:20 PM
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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
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Old 08-09-2020, 07:35 PM
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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....
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Old 08-09-2020, 08:12 PM
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Quote:
Originally Posted by patrickt View Post
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.
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Old 08-09-2020, 08:17 PM
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Quote:
Originally Posted by patrickt View Post
Yeah, that looks pretty good. Summit will have it at your door by Wednesday,
https://www.summitracing.com/parts/h...5/applications
Just ordered it. Thanks!
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Old 08-10-2020, 07:32 AM
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Quote:
Originally Posted by patrickt View Post
The rebuild kit will come with a couple of different N/S combinations. It will also have all your gaskets. On my Holley, two of the needle and seats looked like they were an exact match. One was .110 and the other was .097, but the instruction sheet that came with the kit indicated that the .110 was the correct match for a needle and seat marked with an H on it (which my needle and seat did). Here's a tip: Put a dab of Vaseline on the black O-ring; it makes the job way easier.
Why Vaseline and not just grease or a dab of oil? Is this to lubricate the new O-ring such that it slides easier into the chamber of the fuel bowl during installation?
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Old 08-10-2020, 07:51 AM
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Originally Posted by SBSerpent View Post
Why Vaseline and not just grease or a dab of oil? Is this to lubricate the new O-ring such that it slides easier into the chamber of the fuel bowl during installation?
Yes, lube up the O-ring so that it slides in and sits nicely. There's probably better lubricants, but I've used Vaseline on them since I was a young teenager (and I'm now in my 60's). It's never let me down yet.
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Old 08-10-2020, 08:04 AM
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Quote:
Originally Posted by SBSerpent View Post
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.
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