1968 Mustang 302 trouble shooting surging and stalling. - Ford Mustang Forum

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post #1 of 5 (permalink) Old 08-04-2009 Thread Starter
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1968 Mustang 302 trouble shooting surging and stalling.

So I have been slowly and progressively illiminated many possible problems but still end up with the same symptom. I have a recently rebuilt 302, with a 570cfm holley street avenger, stock heads, weiand intake, mild comp cam, and stock ignition system. My problems started when the engine started surging, only noticeable when the car was in neutral and i reved the engine, to about 2,000 rpm. Later the car started stalling and i had to play with the gas to get it to run, now the car wont stay on unless i have my foot on the pedal. Ive done the following things but still havent found the solution:

1. changed the inline and internal fuel filters

2. set the timming to 6 and then advanced it to 8 since the cam is a mild one

3. changed the distributor cap and rotor

4. checked for vacumm leaks around the carb base, and intake, and hoses

5. replaced the PCV valve and hose

6. set the mixture screws to the highest vacumm reading using the full vacumm port

7. Checked the float level on the side holes, and it was were its suppose to be

So now I have removed the carb. and Im debating over rebuilding it, or just buying a new one, of another brand. But I noticed something while I was removing it, and was wondering if its nothing or its a sign that could lead me to whats wrong, I saw that there was some type of brown residue, like when oil gets burned on hot metal, but not actual oil. The attached pictures are that of what I saw.

Ive also been told that a sticking float could be causing this problem, so Ill get back when I tear into the carb. But any other ideas or solutions would be greatly appreciated.

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post #2 of 5 (permalink) Old 08-04-2009
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before you sell the carburetor why not take it to a carb shop and have them trouble shoot it ON the car. Might save you some $

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post #3 of 5 (permalink) Old 08-04-2009
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ok just to say i had problems like this very similar b4 and it was all carb problems. good motor, dirty carb. If you want to peice it apart to clean it good and rebuild it (not that hard) go right ahead. if you'd rather try some other stuff to the carb b4 peicing it apart i'd tell you to remove the idle mixture screws one at a time and take a can of carb cleaner and spray down that hole. you may use copressed air also. oddly enough if these are clogged it can give you hell....when i took my carb off and peiced it apart to put a new accelerator pump in it the thing was looking nice but when i put it on the idle was crazy...and that wasn't even my original problem. peiced it apart and cleaned it again....and still then i sprayed just a bit down the mixture screw holes and purr'd like a kitten. but lol thats a little off subject but try that b4 peicing the thing apart.
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post #4 of 5 (permalink) Old 08-05-2009 Thread Starter
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Ill give that a try, I took off the carb. and will be working on it this weekend, hopefully I find out what the problem is.
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post #5 of 5 (permalink) Old 08-06-2009
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While you're inside of the carb, check the diaphram on, or replace the power valve. Make sure that it isn't sticking or loose and its gasket is sealing. Holleys have a problem with the idle and main circuit air restrictor orifices (Bleeds) often getting clogged. These are the two small openings just above each venturi. (8 in total) The ones for the primary venturies are inside of the choke horn. These can be the problem. A main jet that has worked loose is another.

You could have a fuel pressure or delivery problem, (A kinked fuel line, a clogged screen on the fuel pickup in the tank or an internally collapsed hose can affect delivery and volume). There may be water in your fuel. Did you start getting the problem a short time after buying fuel?

As for the brown discoloration on the carb and manifold. Looks to me to be from oil vapors that have entered the carb from the PCV valve.
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