I have a 1973 f-100 with a 302, motorcraft 2100 2bbl eletric choke, and an automatic transmission. Everything on the engine is stock.
I had the carburetor rebuilt but the engine still won't idle well, it won't idle at all when cold and misses when it's warm. It also hesitates if you really give it gas.
I finally took it to a mechanic and he thinks I need a new carburetor. He recommended a Holley 500cfm. Would that be too big for a stock 302? Do you think I even need a new carburetor or is it something else? All the vacuum hoses are good, it probably needs a set of plugs, however. Also has a new fuel pump and filter.
Any help would be appreciated

 

Is it timed correctly? One common mistake is to compensate for late ignition timing by opening the butterflies too far, idle mixture screws etc so it will sort of idle OK. Hesitation can be the result as well, also check for accelerator pump action (engine off) should see a couples squirts doen the carb throat as soon as throttle is actuated.

Make sure timing is correct, float level, and idle mixture. Check that buttterflies are closed or nearly so, and only the idle slot is exposed at idle.

 

Take the truck over to the cat that rebuilt the carb and have him make good. My guess is he cleaned it up some, threw a $20 kit at it and called it good. Did he replace (or even check) the throttle shaft bushings? Accelerator pump diaphragm? Float(s) for leaks?

Have you done everything you can to make it run right? Your mechanic checked it all out before suggesting a new carb? Initial timing, timing advance, choke operation, firing order, etc. Did he say why he thought the carb needed replacement...what exactly was wrong with it?

Anyway, 500 cfm will work fine on a 302. A 600 cfm 4v will work better and cost about the same...it's the intake manifold that'll break ya.

 

If the carburetor was rebuilt correctly, why does the mechanic think you need a new carburetor?

The only weak area that would be a showstopper, high mileage worn carburetors, the throttle shafts will cause excessive wear in the carb body and allow for vacuum leaks.

Mikes Carburetors (there are others, too) webpage has free downloads of the manuals and instructions. Carb setup isn't difficult but it's got to be done step by step.

Float level and the fuel level in the bowl is another common error that will cause trouble. A misadjustment there means other misadjustments farther down the line to try and compensate for the earlier problem.

If the carb is in good shape there's no need to replace it. This page is for a Holley but has some good setup tips and common errors in basic carb setup. Take the time to set everything up step by step and it will purr. Let us know what you find.

http://www.junkyardgenius.com/holley/tune01.html

 

Thanks for the replies, gonna put plugs/wires/points on it this weekend. I provided the kit and it was a motorcraft kit. He said he put a new accelerator pump in it. The choke works correctly. I asked about the timing and he said that it was good. I don't know how to check firing order. It's over my head.

The carburetor was full of rust from the old gas tank I had on it. He says the
Carb is "worn out". I doubt he was saying that to scratch more money out of me, he is covered with business, and knows that I can replace the carb.

Will I need a new manifold if I use the Holley carburetor?
Also, the engine was rebuilt in '93 before I owned it. I do not know if the PO put a new carburetor on or not. But it sat with gas in it for 5 years before I got it, and it has 142,000 miles total, 15,000 since the rebuild. I'll check all that stuff when I get back to it today

 

Ok, lets calm down folks. A Motorcraft 2100/2150 does not have throttle shaft bushings. The shaft goes through the body of the carb. This area and the shaft can get worn, especially after 40 years or so of use. If you had rust chunks in it after the rebuild of carb, you need to replace/clean your gas tank and install an inline fuel filter, a good one.

I would skip the Holley and get another 2100. They are one of the simplest carbs to work on and cost half the price of a Holley.

Ford Truck Carburetors

 

I second the "replace with stock" idea... after a tuneup and make sure it is getting clean fuel.

The 2100 works well and you won't have to adjust wires, linkages ect. I used an Autoline brand reman on my Dent from Autozone. Bolt it on and adjust the idle. It has worked fine for several years.

 

i vote for a new carb..I had a 78 motorhome with a Ford 460 in it that ran like crap/rich and kept failing emissions.. I tried rebuilding the carb myself, and it made no difference on the emissions test...I tried a reman motorcraft carb from checker auto(now oreilly) and the test came out even MORE rich at idle...took it back to the parts store and the guy recommended an edelbrock/aftermarket carb..I went with this option, and the engine passed the emission test with flying colors and ran great..I now use a Holley carb on my 77 f150's 460 and I am very happy with it.. it was darn near perfect right out of the box!

However.. before you go chasing carburetor problems, make sure the ignition system is in good condition...how is the coil? you might want to replace it(cheap) or at the very least test it..a weak spark/coil can cause the problems you are having.

 

New distributor cap, rotary button, points, plugs, and wires and she's running great! Thanks everyone for the help! I ran all the carburetor tests anyway and they all checked out. Probably not going to go back to that mechanic

 

Good deal. "90 per cent of carburetor problems are ignition related."

 

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