I've got a sweet spot on my T mixture control knob for lean. However, with car vibration (a given) the knob likes to creep a bit to the rich side. It's tolerable, so I live with it but would like to improve the situation as the touring season is here.
What are your best methods to control mixture knob creep, please?
Does your carb have a "nut " at the base of the mixture control shaft?
If so just tighten the nut like on a water valve.
Herb
I use a rubber band around the shaft of the knob and it rubs the dash and holds mine in place. Simple but it works for me.
Bob
Bob Mc Daniel. rubber band! SMART! I like simple. You are a "T" man for sure
Mike Hageli
Elmhurst IL.
I use a piece of black shrink tubing. As a bonus it helped remove another rattle. Only 15M more rattles to eliminate.
I'm no expert, as I am only familiar with the earlier non-swivel type NH's, but do other carbs not have the nut at the top like Herb was saying?
One problem with those, though, is that the shaft of the needle valve becomes worn where the friction lock is. Over the years, people have tightened it more to keep it from moving, and eventually there's a delicate balance between too loose where it runs most of the time and too tight anywhere else (Like trying to seat it all the way down to count turns open). The added friction will mask the fact that the needle is bottomed out and people will seat it too hard and ruin the needle and seat.
John, what carb are you using?
Hal -- Just loosen the nut when you want to turn the needle down to the bottom, then re-tighten it afterward.
Mine tends to vibrate to where the little pointer part of the knob is at the bottom. Probably due to the added weight there. I find the sweet spot, and if the pointer is at other than the bottom, then I pull the cotter pin and rotate the shaft 1/4 or 1/2 turn in the square tube on the carburetor adjuster so that the pointer is at the bottom and re-pin it. Of course this is with the '26 style swivel on the top of the NH carb. This might not work with the earlier style swivel.
Mike,
You and I know that, but from what I've seen on some carbs, not everyone does.
Erich ~ I've got a Holly NH carb just like the '21-'23 one on the upper right corner of page 423 in Bruce W. McCalley's book.
The mixture control connection point has been modified with a universal joint typical of later carbs, for pull and turn performance at the dash. The carb is mated to a 1925 engine. The body of the car is from 1920. Yes, the bell crank from the 1920 model is still on the firewall, in case I ever want to return to separate mixture/choke functions.
I like the rubber band idea best. Simple.
A T friend suggested buying an aftermarket star gear (from a rear brake kit) & modifying it for fine-tuned mixture performance at the dash. Opinions, anyone?
Saw a carb control modification once at a T show here many years ago. Fellow had a nickel-plate clock arm that had motion over a reeded metal arc. You moved the bar to the appropriate notch on the arc and had no more creep.
Thought I had a photo of the clock arm on the metal arc. Can't find it so maybe not.
Anyway, drove the T on its maiden voyage with the rebuilt engine this weekend. 52 miles, mostly rural highway. Beautiful, scenic. Lots of waiving at passersby.
I may be missing something on this thread but if you're having trouble with your adjustment needle moving while underway, snug the packing nut "Needle valve lock screw". As mentioned in the above posts. You can make it so tight, you can't even turn the adjustment screw, so be sure not to over tighten it. This will allow you to do away with all the other home remedies that just complicate a minor adjustment.
Hey there J Berch ~
Thanks for the reply. The needle valve lock screw is snug. The problem is with the mixture control rod. There is enough play in it that at the dash, it likes to creep 20 degrees to the rich side.
John
I guess I'm still lost. The needle valve and the mixture control are the same thing. Am I missing something?
Seems plain enough here Hal. If you tighten the needle valve lock screw there's no way the mixture control knob can creep !
schuh
I agree, but John seems to be saying the problem is not with the lock screw, but with his mixture control rod. To me, one is an extension of the other. I don't see how one can turn independently of the other. Hence my confusion.
Could be the lock nut (screw) is just flat worn out and bottoming leaving the needle valve loose. You could remove the nut and grind about 1/16" off the bottom and see if it will hold better.
My 23 Fordor did that until I replaced the needle valve and lock nut with a new one.
John -- If the rod's diameter is worn enough at the point where the nut is, it may be that the nut's 4 sections are binding against each other when it's tightened, rather than on the rod. You might need to take the rod and nut out of the carb and run a hacksaw blade down into the nut's slots to widen them just a bit. Then the nut should get a bite on the rod.
Dick,
"My 23 Fordor did that until I replaced the needle valve and lock nut with a new one."
You must be new to Model T's or some kind of rebel. Model T guys never replace anything when rubber bands, hack saws, shim stock, bungee cords (which I have used extensively), or JB Weld can be used instead.
John, I also like the rubber band idea,I once used a rubber band to repair a broken in half tie rod on my T it was supper cheap and simple! I am sure they can fix anything on a T and am thinking to use them to repair my old rotten wood wheels also!
All kidding aside My T's are one of my most treasured possessions and I would never think to install a rubber band or any other quick fixes. Replace the worn parts Your car has lasted almost a century does it deserve the very best.
You know the answer.
The 26-27 type has a pinch spring at the swivel on the top of the carburetor. It is possible that needs to be pinched with a pliars to tighten it.
Also, are you sure that the mixture nob is actually creeping? If you have a leaky float valve, it is possible that the fuel levels change as you drive, which will also richen or lean the mixture. When at idle, or parked for a short time, the fuel level will rise, and when driving with an open throttle, the fuel level will drop. This can be quite confusing, because just as you think you have the mixture set correctly, you drive a ways and it is either lean or rich.
Norm
I guess I should say my rubber band idea was used on my 26 because I had one at the time and was driving the car and saw the knob turn. I forget how I had to fix the problem now but for a quick fix while on the road it worked great and I still keep one in the car in case it moves again and I don't have time to pull over and fix it right then. I also carry a coat hanger and a few other little items in case I need to fix something else on the road. I have used the coat hanger in my modern car to hold the exhaust up when it broke and drove home that way. Now I carry one in all my cars. I am not saying this is the only way or even the best way to fix something but it is a temp fix and hurts nothing. At least it works till I find time or learn how to fix it right later. At least I don't buy a waterpump to fix a bad radiator or a distributor to replace the coils but I do use my right hand to crank start my car so I guess I do a lot of things wrong but then again, I like doing things my way.
Jerry
I only did it to help keep the vendors and the USPS in business dogone postage cost more than the parts BTW you forgot to mention duct tape
I am with Hal Davis, I don't understand what the problem is, Tighten the lock nut and be done with it.