Any help greatly appreciated.I rebuilt this carb (4100) and can not lean it up.Runs so rich it actually runs better with open vacuum at intake.What do I look for? Is this old carb just wore out? The car hadn't run in 13 years.I saw the last owner was running it with a open vacuum at intake so this is a old problem.Old cars are so much fun...........
The easy answer is to replace it with a new 600 cfm Holley. But from a diagnostics side, do you know where the extra fuel is coming from? Are the main jets to big? Perhaps a stuck power valve or choke? Check out this link for a 4100 manual. http://c807991.r91.cf2.rackcdn.com/autolite_4100_manual.pdf This diagram may help.
Pull the power valve cover off. If there is fuel in there you probably have the wrong valve or gasket causing a leak.
In the diagram make sure that #9576 is in the accelerator pump housing. It's just a little rubber plug looking thing
The elastomer valve (9576) won't cause his problem but the power valve will. If the carb hasn't been kitted since sitting that long... rebuild it. They are super simple to do. You might have problems finding the secondary diaphram, it isn't in the kit for some reason. What is real cool about these carbs is you can remove the top and fire it up!!
What brand kit ???? I haven't done one in a while, but the last two the customers brought the kits and they didn't have them.
My vote is the power valve too. Blown or wrong one. A Holley power valve will not work (very long) in a 4100. If its an early 4100 the 9576 won't be rubber. They used a check ball set-up. Very simple, reliable carb. If your not racing the car it's the best carb to run on the street IMO.
Floats out of adjustment, or a stuck/dirty needle and seat will cause an over rich condition as well. Fuel dripping from the boosters at idle is an easy way to spot this one. As said, you can run the engine with the carb top off, so it makes fuel level adjustment easier.
Rock Auto has the Motorcraft kit for these for $20.00 ... it is supposed to have the secondary diaphagm in it. Walker is the kits that don't have them.
When you have tha carb apart use some fine sand paper on a dowel to smoothe out the casting line missmatch most of them have down the bores.
Has to be either a blown power valve or over sized jets. Sometimes people swap in booster venturis from other 4100's and 2100's too that can cause other issues.
The gskt underneath the booster venturi is lower than the correct fuel level in the float bowl. If this gskt is leaking fuel will constantly drip or run out of it going directly into the carb throat causing a sometimes hard to find very rich condition. Greg
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