Carburetor Fuel Leak - Team Camaro Tech
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post #1 of 4 (permalink) Old Jul 10th, 12, 12:23 PM Thread Starter
Join Date: Mar 2012
Location: Texas
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Carburetor Fuel Leak

Hey everyone i really need some advice on a fuel leak that I'm having. I bought a brand new Holley Ultra Street Avenger 770 for my 454 and recently noticed its leaking fuel. Notice it only happens when i shut the engine off

Its leaking fuel from the tiny vents right above the secondary throttle plates. It's only on the right side really, and because of this its seeping out of the secondary throttle shaft and pooling on my intake.

I've tried everything i can think of. The float needle and seat are fine, the base is tight, i even took the bowl off to find debris and there was nothing. I havnt taken the metering block of though. So the float bowl is as far as I got.

using a carb spacer as well, i dont think the fuel necesarilly boiling, it happens regardless of how long its run. 1 minute or 1 hour its the same.

please help! ill post photos if needed!
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post #2 of 4 (permalink) Old Jul 10th, 12, 03:20 PM
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Re: Carburetor Fuel Leak

I wouldn't even bother trying to fix it. Holleys are lifetime least the last time I bought I'd trade it in.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
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'69 Camaro Beater-SFT 327-M20-Moser 4.10-sold
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post #3 of 4 (permalink) Old Jul 10th, 12, 05:51 PM
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Re: Carburetor Fuel Leak

What's your fuel pressure and you didn't mention whether or not you checked the float level.

69 SS, 350/300 h.p., M-20, 12 bolt, matching numbers.

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post #4 of 4 (permalink) Old Jul 10th, 12, 11:21 PM
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Re: Carburetor Fuel Leak

1)First thing i would do is pull the needle and seat oyt and inspect the O rings on them.Look for any signs of wear or cracking.

2) Set the float levels to bottom of sight glass. Fuel should not be seeping out.

Note: make sure you have some replacement gaskets for the adjustment nut and screw as these will most likley tear when you adjust the floats. The nylon washer set is a better way to go as they are reusable. Nothing worse than being held up because of a paper thin gasket.

3) Make sure your timing is correct so you are not causing a lean condition. (fuel boiling)

4) Keep an eye on your Vacume secondary pump housing and shaft. Is there any fuel dripping from it? You may want to check the diaphram for damage. If carb has been sitting for a while these parts dry up and become brittle.

5) Check your fuel pressure! These carbs can only take 7psi before you start running into issues. Have you replaced your fuel pump of late and if so with what?

6) also look at the base gasket when things are running. Is there any fuel leaking out or do you hear any hissing sounds that would point to a vacume leak or a blown gasket on the base plate to carb body which they are prone too.

7) what is your vacume reading at idle with hose from distributor plugged? What is the power valve that is in the carb at present? Have you changed it or someone else?

8) have you recently had any head work done? Are the valves set properly? A sticky valve or incorrectly set valve train will allow back pressure to the carb.

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Last edited by 67RSSS; Jul 10th, 12 at 11:42 PM.
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