Single Barrel Carburetor Problems On Antique

How about make model and date of manufacture my crystal ball is broke.

1948 ford F1 226 engine, holly carb. no numbers

S

Youve got a crystal ball as well, i just need to replace the batteries in mine

This link is for hollys

http://www.google.co.uk/search?q=holly+carb&hl=en&rls=com.microsoft:en-gb:IE-SearchBox&source=univ&tbs=vid:1&tbo=u&ei=JubOS8CXKZOImgOs2_ke&sa=X&oi=video_result_group&ct=title&resnum=9&ved=0CDoQqwQwCA

thanks much the old 48 will appreciate the work

A vacuum leak can cause erratic idle.

Use a section of hose to look for the leak by sound.

I had a 1948 Ford not so long ago. Six volt system , flathead , I didn't have the

gearbox , and I put it up for sale , but , as I recall , parts are virtually unobtainable ,

and ignition parts especially.

I just totaly rebuilt the entire brake system all parts are available from Dennis carpenter, LMC Macs auto parts, and several others.

Carb. does not have vacuum leak, bottom throttle plate and shaft are worn, carbureater USA is going to rebuid and replace throttle shaft.

Also just redid the entire starting and ignition system also all parts are available with no problems the truck starts great!!!!

I agree to look for a vacuum leak around gaskets between carb & manifold. Older engines on occasion develop this problem. I had this problem about 33 years ago.

"I agree to look for a vacuum leak"

The fastest most reliable method I have ever used for finding vacuum leaks was a basting bulb filled with gasoline. With a CO bottle close at hand I slowly dribbled gas onto the manifold. When it found the leak and got sucked into the engine you could hear the idle jump immediately.

In later years when nervous managers prevailed, I'd use gasoline mixed with kerosene. The sudden smoke from the exhaust was not as quick but it worked.

L.J.

Better than gasoline: Use an unlit propane torch and direct the propane around all bolts, gaskets, etc. A speed-up indicates a leak. Heard this from a carb man.

Agree with the vacuum leak proposal. Used to use a can of spray carb/choke cleaner and sprayed around the base of carb and/or any vacuum hoses, usually gives fast accurate results .

I gave you a GQ for this question. Most likely cause, most carburetors have an external dash pot specifically to handle this kind of situation. The dash pot prevents the throttle from closing rapidly. I suspect yours needs adjusting or replacing. Either way, it's a simple fix.

no dash pot, no vacuum leak at gasket.

the lower throttle body shaft and butterfly are the suspect at htis point

Congratulations!! You just solved your own problem. Someone stole your dash pot. Seriously, fit a dash pot to the carb, and I suspect your problem will disappear. Your symptoms are why dash pots were fitted in the first place.

you are correct on the throttle shaft and body leakage, there are press in bushings available for most sizes or make you own from brass stock and ream to fit after drilling the body for accurate alignment, will be as good as new, the dashpot fitted to later engines is to prevent backfire on rapid decel as the fuel has momentum and continues to flow briefly causing over rich and boom,

It sounds like there could be a burr or carbon build up in the throttle body where the butterfly closes.

I would check for worn throttle shaft bushings first if idle is affected by touching the throttle linkage.

Try the mentioned propane test. Turn on the propane but dont light it , with engine running, place the nozzle against the shaft bushings and listen for a rise in idle .

Let us know what you found.

your idle jet is clogged