Author Topic: Carb tear down, new problem  (Read 2298 times)

Offline 1 Fat Cat

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Carb tear down, new problem
« on: August 26, 2016, 09:03:27 PM »
I had my carb rebuilt by Cliff about a year and a half ago. When I installed it this summer, it ran great after just a minor idle adjustment. However, I had the following issues::

- Difficult hot starts after sitting 15-20 mins
- Leak all around top air horn gasket
- Running out of fuel at wot

Decided to crack it open and with the assistance of Cliffs book go through and check a few things.

- Checked for leaking bottom plugs. They were epoxied and passed the pressure test
- measured float level at 5/16" so I set it to 1/4"
- Air horn warped at two mounting bolt holes. Stripped down and sanded it flat

Put it back together and went for a spin today and noticed the following::

- Idle was rich. Not sure why since nothing changed unless due to higher float level?
- Leaned idle and went for a drive. Every time stopping the carb would load up real bad and almost die without feathering it for 10-15 seconds until it would clear up and idle decent again.
- Was able to make it farther at wot though still ran out of fuel at higher speed. More fuel in the bowl helped but still need more volume?
- Gasket and upper main body still getting wet from fuel leak. Seems to happen more when sitting after shut down

Any thoughts or suggestions? What would I have done wrong or missed to cause the loading up when stopping?

Offline carmantx

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Re: Carb tear down, new problem
« Reply #1 on: August 26, 2016, 09:44:34 PM »
The wet gasket is possibly from float to high, so you might try lowering it some. 
You don't mention engine or intake, but you may need to use a metal heat gasket between carb and intake to keep it from getting so hot.  The fuel inside is probably boiling after hot shut off.

Check your fuel pressure to carb, and make sure filters are clean.
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Offline von

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Re: Carb tear down, new problem
« Reply #2 on: August 27, 2016, 01:40:04 AM »
The symptoms sound to me like too much fuel pressure. I found that most aftermarket fuel pumps sold at chain parts stores have too much pressure for a Q jet to handle. BTDT. An AC Delco pump fixed that for me. Also make sure you don't have a leaky needle and seat. Sometimes if the seat gasket surface of the main body is damaged or if an old gasket is mistakenly left under a new one a leak can occur between seat and main body.

Offline 1 Fat Cat

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Re: Carb tear down, new problem
« Reply #3 on: August 27, 2016, 09:00:38 AM »
Thanks guys. I think I mentioned my motor and fuel system in another post. I've been through the filters and fuel pressure already. I didn't change anything since opening the carb up yet now I'm having this stalling issue...

Also the needle and seat are new from Cliffs rebuild though I did vacuum test and it held 20"hg.

Offline Cliff Ruggles

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Re: Carb tear down, new problem
« Reply #4 on: August 29, 2016, 09:32:40 AM »
Running out of fuel is not cured by float height as you found out.  The fuel system is not keeping the carb full on hard runs.  With the .135" N/S assembly you should be able to keep up pretty easily.

What is the fuel delivery system.

What are the engine specs?

Acting up when you slow down, stop and let the engine come to idle sounds like a flooding issue to me, or high fuel level, or both.....Cliff