Hello, I have a 350 chevy engine with a fairly standard carter AFB carb. I have been having trouble for some time figuring out why one side of the carb will not provide enough fuel at idle. If I squirt fuel into the left side of the carb the engine idles normally, when I stop it starves the 4 cylinders fed by this side of the carb. The engine has an intake that separates the plenum under the carb so each side of the carb supplies only 4 cylinders. When no fuel is added to the left side the cylinders fed by it do not fire which I checked by pulling wires to those cylinders and there is no change in engine rpm but there is very noticeably with the right side. I have dismantled, cleaned and rebuilt the carb and nothing seemed to change. Any help will be very much appreciated. Thank you!
Actually what youa re having is worng, there should be 2 cylinders on one side and 2 cylinders on the other side that don't fire. But it sounds like a vacuum leak. Your carb may need a rebuild to fix this. Or your metering jets can be plugged on one side not allowing fuel to distribute correctly. You could try to correct this without a rebuild by taking the idle adjusting screw out on that particular side or both if you care to. Spray in choke cleaner and let it sit for a few minutes. Then spray some more in there to clean maybe some junk out and put your screws back in. When you do this lightly seat the screws, you aren't trying to hold something in with them. Back the screws out 1 & 1/2 turns and start the car. Hook up a vacuum gauge and get the highest reading on vacuum that you can. Of course you should also do a compression check to make sure something else isn't wrong. If it still misses, before you redo the carb, pull the valve cover off on the offending side and see if the valves are working ok, you might have a bad camshaft/lifter combo. Oh and by the way, 350's didn't come out until1968 unless yours has been changed.
July, 13, 2010 AT 12:33 PM
Thank you for the suggestions. You are right, I may not have explained correctly, there are two cyl on each side that are not firing. I will try this process again, I have removed the jets and flushed with carb cleaner as well as removed the mixture screws and done the same. I did a compression check and all cylinders are about equal, I have also removed the valve covers to observe the valves operating just fine. I even rebuilt the carb and it seemed to clear up for a very short time but I am right back where I started, still when I squirt fuel into the left side of the carb the engine runs smoothly. I do not have a vacuum gauge so I may have to go grab one to continue. I may need to rebuild it again, that was the first time I had ever done it, though it was simple and I am confident I did a good job.
You are correct this is not the original engine.
Thanks for your help and I hope to ask more questions as I go.
July, 13, 2010 AT 7:44 PM
Ok it really sounds liek a vacuum leak now. One thing I forgot to mention is the metering rods. If I reember correctly the carter has the metering rods held in by a screw in the center of the it. Towards the front. What you could do is take the screw out but have a magnet there so it doesn't go down inside the carb or intake. Take the metering rods out and watch out for a spring as there may be one beneath the metering rods. Check to make sure the metering rods aren't bent or stuck. Also take a flashlight and look down the rods to see if there is a jet in there. Better yet take the carb off before you do this. If you take the carb off yo u wouldn't need to worry abou that. Make sure the body of the carb is flat as well as the base. It may be leaking there. Another way to check befor eyou even start is to start the engine and spray choke cleaner around the side that you spray to see where the leak is.