I posted a carb question a few days ago and just put on my new carb. the problem is I cant get the idle to come down. it drops off the high idle when the choke opens and the idle ad. screw is on the stop. when i turn the idle down till the adj screw is loose it is still high(i don't have a tach but I'm guessing about 1500+ rpm) I tried dropping it down with the timing but then it runs like crap.
I can set it down some with the air mix screw but it idles rough. aside from the idle it runs out great.
Any thoughts would be appreciated. ???
Joe
Ignition timing? Vac leak? Spark advance?
Bill
Bill
thanks for the reply, I run a dual point dist. with no vac advance, I will check for vac leaks when it stops raining
Joe
When the fast idle drops, are you sure that the fast idle cam is actually moving completely out of the way and is not still making contact with the screw?
It's possible that while the idle IS dropping considerably, you could still be on the very last step of the fast idle cam, which would be keeping the throttle open far enough that adjusting the curb idle screw wouldn't do much of anything.
might have to adjust the auto choke. if set totight i will keep the carb on the fast idle setting even if it does warm up
Thanks for the input.
the choke is fully open and the high idle cam i not in contact with the high idle screw.
I'm thinking vac leak. will check today after work
Do you have a de-acceleration valve??? If so, try this...
With the engine running put your finger on the bottom of valve and look for the vent hole. If you block the hole and the motor slows down or quits, you have a bad diaphragm in the de-acceleration valve. This is your vacuum leak. You can replace it or block it off. You don't need it except for pollution control.
The best fix is to remove it and block off the manifold. To do that, remove the de-acceleration valve. Turn the big nut on the intake manifold. Now remove the valve and cut the hose going to the carburetor. Take the valve into the garage and saw off the threaded portion. Now tap the hole 1/2-13. Then install a short 1/2-13 bolt & washer with teflon tape. Now re-install this modified piece to block off the intake manifold fitting. Now plug the hose going to the carb.
After this you will need to reset your idle speed and mixture. It will purr!!!
IF it's the decel valve just remove it then take a hex wrench abd remove the fitting in the manifold and plug THAT hole with a standard pipe plug. a lot less hassle than cutting and tapping
Thanks for all the responses.
It was the de-acceleration valve, apparently it has been leaking.
I pulled the engine out of a donor car and ran the carb that was on it.
the carb must have been set up to mask the leak. I put a plug in it, reset
the carb and it idles great.
Joe