All right.. I am a new Mustang owner and not much of a mechanic so I am learning as I go. I have a 66 Mustang GT. It has a Holley 725 CFM. It will start a little rough and usually sputters out on the first try. Once it gets going it has a little sputter and hesiation when hitting the gas. After about ten mintues it will flood out whether its driving or just idiling.

I live at about 7000 elevation so I lowered the jet size to 64 on the front and 74 on the rear. It still floods. I completely drained the bowls and lowered the floats quite a bit and it still floods. I checked the needles on the floats and they are clear of debris.

I'm not sure what to do next. Please any ideas would be helpful.

 

get an 640 Hp engine to go with that carb...problem solved!

 

By flooding out, do you mean flooding or totally fouling the plugs?

When you remove the fuel bowl sight glass, does fuel run out?

Have you adjusted the idle screws?

The jets only come into play with the respective boosters are sending fuel due to signal. At idle, neither primary nor secondary circuits should be flowing fuel. That probably is not your problem.

 

When I take out the sight plugs fuel will only come out if I rock the car.

I adjusted the idle but it is still doing it.

It seems to do it almost always immediately when I put the air filter back on.

 

Is the air cleaner messing with the choke linkage causing the choke to close and stalling the engine?

 

aye. check for the linkage at top of carb that operates the butterfly. that might interfer with your aircleaner. and obiously make sure the air cleaner is actually clean.

my Demon carburetors for example are a nightmare for this.
725 cfm is a _lot_ for a 289/302 (depending on engine, i guess stock-ish). it will not cause the problem you describe, but it seems to big a carb for me

 

I was thinking it might at 7,000 feet. Not real sure though.

Maybe we should go back to basics and ask...

1) When did it last run right? if ever.
2) What engine and what specs
3) how many miles are on the engine

-Gun

 

I think I got it. The air filter is one of the oval ones and it was covering the primary bowl vent of the carb. I was able to recreate with the filter off by covering it up with my finger. I guess this created some type of vacuum issue.

I'll probably get a smaller carb and new type of air filter. Any thoughts on size of carb, I was kind of wanting to stick with Holley.

 

What are you engine specs? Its not producing 500+ Hp is it?

If you are in the 220 to 300+ RWHP range a holly 600 should do you just fine and they can be tuned in pretty well to match your engine and altitude.

-Gun