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Carb problems

3K views 6 replies 4 participants last post by  72Custom500 
#1 ·
So I have a very old 351W (209,000 miles on it) running on 7 cylinders, one problem at a time. I got a brand new Tomco Motorcraft 2100 replacement carb. All the parts are the same from the Motorcraft to the Tomco. I have the carb properly jetted, took the jets (43F) out of the old car which idled really good at this altitude, I live in Sedona AZ, and put them in the new one, how ever with the new carb it idles really high and I can even back the idle screw all the way off the throttle bracket and the car will still idle at over 1000 rpm. Do I need to put a new power valve in, should I just use the old one or get something new? All help is appreciated. Also the other jet sizes I have are 48F and 53F.

UPDATE:
I did a manifold vaccum test and the needle rapidly shook from 10-13inHG at idle and dropped when revved. don't know if that is because of power valve or what, I really need help with this because this car is my daily driver.
 
#3 ·
Something doesn't make sence. did you take the jets out of the old carb and put them in the new carb ? If so why ? A bad power valve will not cause high idle it will make it run
rich. Do you know what the power valve does ? What you describe on your vacumm gauge is you need a valve job. Need more info.
 
#4 ·
Ok so the car has never been rebuilt since 1972 and the engine runs, but it could use a valve job, right now I'm just trying to limp it to summer time so I can get it rebuilt. The carb I took off when it was Idling good was a motorcraft 2150, i don't know it that will help. Also cylinder 6 is the one that needs the vavle job, it doesn't hold pressure and the spark plug is always pitch black. The jets from the 2150 were 43F and I put them in the 2100. What I noticed on the carb is the butterfly valves don't seal very well at all which is probably the source of the problem. Any Ideas?
 
#6 ·
Sounds like a big vacuum leak in addition to the cylinder that doesn't hold pressure.

You need to make certain that every possible vacuum port on the manifold and the carb are either used or plugged and the used circuits must be checked to see they hold vacuum.

Also check the carb mounting area. - BA
 
#7 ·
Thanks guys I really learned the meaning of "If it ain't broke don't fix it." I switched back to the 2150 and all was fine. If anyone happens to need 1-3 motorcraft 2100's I just happen to have a few. *facepalm* Well now I can focus on the upcoming much overdue rebuild.
 
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