Have a 1927 T with a rebuilt carb from Russ.
Center drain NH.
New rings and glands and new exhaust manifold.
Always have to have the mixture knob open around 2 turns for smooth running. Usually 1 3/4 is about the smoothest. Using a hot air pipe. Rebuilt carb with cleaned passages, smooth needle surfaces, etc.
Anyone have an idea on why I have to have it open so much?
Always have been like this. I have only got it really running two weeks ago .
Should also say, it's not necessarily "rich". But it's like it's normal 1 turn on other Ts is 2 on mine I think?
I believe the common wisdom that they're all different may be at play here. That applies to carburetors as well as cars. The NH I currently have on my runabout runs best at less than one turn, about 7/8. Other carbs I've used needed 1¼ or even 1½. Yours needing a little more may be unusual, but if it works I wouldn't worry about it.
It's only "rich" if your plugs are getting sooted up.
Run it where it is smoothest. If you had a smooth idle and rough at higher speed or smooth at higher speed but rough idle, I would suspect a carburetor problem or intake leak, but if it runs smoothly at all speeds it's OK. I think if the carburetors made in the Model T day had been as precise as those made today, it wouldn't have had an adjustment. But Henry had the adjustment because he knew that you could fine tune it.
Thank you everyone. Plugs are clean. Must just be how mine is... Probably still in the "break in" stage as well. Who knows how long it's spent sitting in a barn.
It runs wonderful. Where I set it (at about 2 turns), is great. It's smooth at all speeds. No red exhaust or overheating. It's running on the co side even on the Moto meter (I've only gone on short mile trips though.
Thanks all, figured I'd ask. Better safe than sorry. Just wondering as I haven't really seen any other threads with people opening theirs this much
Easiest way I've found to "fine tune" the mixture adjustment is once the engine is at operating temperature, at a fast idle, begin to lean out (C.W.) the mixture until the engine starts to "stumble" a bit then open (C.C.W.) until the stumble goes away - at that point, you should be able to give the throttle a "quick jab" without any hesitation or popping back.
Remember most NH carbs like a slightly richer mixture for cold starting - 1/4 to 1/2 turn richer from what I've experienced - YMMV.