My '27 has a Holley NH carburetor. It ran normally last year, but this year it had a sticking needle valve that would sometimes stick open, sometimes closed. After taking the carburetor apart, cleaning it, adjusting the float (the level was way off) and reassembling it a half-dozen times, the best that I could do was to get it to run, but very rich (black smoke) with the spray valve adjustment all the way closed. I threw in the towel and bought a rebuilt carburetor from Lang's. The T now runs great, but only with the spray valve screwed all the way in. Any ideas as to why?
I don't understand how the car could run with the spray needle closed all the way. If two different carburetors need it closed, maybe the problem isn't in the carb. But I have no clue what else it could be.
Sounds like you have the same fuel problem with 2 different carbs. Frankly that means you have the same problem with 2 different carbs. Not trying to be funny it's just that, I believe, the parts houses don't do rebuilds but their sent out. Quality varies. You may have a loser there. Same things clogged on both of them. I do my own and when I do they work because their cleaned to the teeth.
A pure guess:
Could it be that the adjustment linkage is somehow binding up? Perhaps when you have the "spray valve adjustment all the way closed" what's actually happening is the linkage is stuck. Try disconnecting the linkage and making adjustments directly on the carb and see what happens.
I've seen this happen. It appears it is completely closed when in reality it isn't. What happens is the adjusting needle nut isn't tightened down completely. This causes the friction clamp of the adjusting needle to catch on the hex of the nut, giving you a false sense of complete GAV closure. Pull the adjusting needle nut and run a 1/8" pipe tap down the carb casting, then take a 1/8" pipe Die and run it over the adjusting needle nut, reassemble and drive the needle down. make sure there is a gap between the needle clamp and the top of the hex of the nut when the needle is seated.
Thanks for the suggestions. I agree with Steve; I don't see how it can run with the spray needle all of the way closed. I'll try Mike's procedure.
And never screw the spray needle down far enough to put a groove in it.
Is the same spray needle the one common part being used on both carburetors? Sounds like the needle tip is tapered incorrectly and not seating properly.
If it has a reproduction spray needle shaft it may be that it is not threaded as far on the shaft of the needle as it needs to be. Some of the new ones are not threaded correctly. Also, a couple of the new carbs I have seen do not have the body threaded full depth. They run out of threads before they completely close the spray needle.
There is a reason the diameter of the shaft changes several times. Some of the new ones do not have the correct diameter of the shaft, either.