25/26 Mixture Control Confusion

[Hudson29]

Sometimes I'm easily cornfused by simple things. The initial setting of the mixture control needle on my '23 is dead simple. The needle is run down until it gently seats then backed off a turn. The split nut is then tightened just enough to prevent the adjustment from wandering from where its been left. On the Improved Cars and even starting in '25 Ford combined the mixture adjustment with the primer/choke control. As far as I can tell reading the Club carb book, the NH was otherwise the same as before.

The man who built my '14 added a motor from a '19 with an electric starter and he wanted to be able to prime/choke the motor from the driver's seat. He devised a way to combine the '14 knob with the 25/26 mixture/primer/choke control. What he came up with is rather clever and works well. Here is what it looks like installed:

I would like to retain the setup but with a new needle. The existing needle has some wear on it that might make it hard to adjust reliably. I ordered a new needle & shaft and collar nut for the 25/26 setup. The new parts for this do not make sense to me. Just inserting the needle into the body of the old carb just removed from the car I can feel it seat as shown in the third pic. With that odd shaped nut run down as far as it will go and the needle run down into the nut as far as it will go it still has not seated. Possibly the bent steel shroud needs to be bent further open to go around the hex of the nut. Possibly that might allow the needle to seat. If so, what keeps the needle in its place? If we bend that shroud in to contact the barrel of the brass nut it might hold the adjustment but the needle would never seat.

What now? Is the casting of the carb wrong? Is the brass nut wrong? What am I missing?

Paul

[Scott_Conger]

I had to blow up the picture to see what was going on, and once I did, it's an easy one:

The new brass fitting is not threaded right. Look at it and you'll see that it is not cut deeply enough and the OD does not have sharp crests like the jam nut on your old one. Since it is a tapered thread, yes, it will go in but will not go in far enough. The thread looks like an incorrectly adjusted Geometric Die was used on the screw machine that made the part. It shouldn't be like that, but running a 1/8 npt die down on it should get it to seat further in. If that wasn't QUITE enough, you can remove a little off of the end of the clamp ears so they don't foul on the top of the nut.

Do not make any alterations to your carb. It's the brass screw-in part which is the bug-a-boo here. And DO NOT OVERTIGHTEN THE BRASS PART TO MAKE IT GO IN FURTHER...doing so runs a very strong chance of cracking the casting. It should be just snug so as to not back out.

Your old setup was just a common needle with the ears bent up and the jam nut remained functional as-is. You have purchased the combination that is correct but got a bum part in the process.

Easy fix

[DanTreace]

To add to what Scott posted.

Think a small part of issue is the repro needle, it is more tapered than earlier repro on my bench test, and that more narrow taper does have to seat further to close on this ‘23 NH. Making it seat may take some creativity.

The older repo seated ok, the newer repro needle collar had to ride over the flats on the swivel nut.

Thin long taper needle of newer repro on top.

[Hudson29]

Thanks Scott, I'll see if I can locate the tap & die set. There are still many things that have not surfaced after the move.

What you said makes sense to get the needle to go in far enough to seat. The pics in the carb book do show the hex of the nut right down to the casting.Those ears on the needle should be bent in a bit to contact the brass barrel to provide some resistance to turning?

BTW, I have absolutely no problem with using the earlier type needle with the T bar & two holes. Could one be accurately bent in a vice? I'd hate to wreck a new needle trying to bend it.

Paul

[Hudson29]

Thanks Dan, the needle collar should not, ideally ride over the nut? Just to make sure I understand, it should be able to pinch the barrel of the nut to hold the adjustment? Possibly I can grind that collar shorter to give it more clearance from the fully seated hex.

Paul

[DanTreace]

Yes, that split collar should slightly drag on the brass cylinder for resistance.

Your fix plan should work, good luck!

[RajoRacer]

I made mine for the same reason - electric start combination using an original Holley G needle - you can do the same with the NH.

[Hudson29]

I had at the brass nut with the 1/8 NPT die and ran it down until the flair under the hex bottomed. A trial fit on the old carb showed that it was better but stiil not all the way down. Inserting the needle confirmed that we still have a problem. Just for fun, I tried the nut on the carb I'm going to use already installed in the car. The fit here was a bit worse than the one on the bench.

Perhaps the nut is too long below the threads? Perhaps if I ground off some of the lower portion it might allow it to seat better?

Paul

[Scott_Conger]

It is a tapered thread. Generally, if it is cut short it will simply be too short. The reality is that it may already be too short, meaning the "small" end is still too big. The next step would be to measure the diameter of the small end and compare it to a standard 1/8 npt plug. I am going to bet your die is a hexagonal rethreading die and not a round cutting die...am I correct? If that is the case, then the face of the die is too tall to work on a part with an obstruction and is intended to be used on a part which does not mechanically limit the amount it can thread on.

There remains another option and that is to run a 1/8 npt tap down into the top of the carb to get it larger to accept more taper. If you do this, don't go crazy with it.

The root cause is that the part you were sold is wrong, simple as that. When making a pipe thread there are some standards involved and your part would not fall within the high/low limit. I've run into this problem with reproduction parts containing pipe threads and the usual result is that they stick out a little more than ideal and do not cause a fitment/tolerance issue. Your situation does.

[DanTreace]

That tall cylinder nut has tapered pipe threads, so trimming it shorter won't let the fatter threads turn down much at all.

You choice may be to trim the ends of the collar, there is plenty of collar to provide grab on the cylinder with a bit of a squeeze on those arms.
With shorter arms, won't hit the hex portion of the nut and allow the needle to go deeper.

Note comparison.....the original collar shown has different shape to arms, and they are shorter. The reproduction collar has bigger and longer arm to get in the way of threading in the needle.

[Scott_Conger]

I won't edit my reply, but looking at your photo again, I absolutely agree with Dan. The fit of the part now is nominally OK and I was quick to judge otherwise. Comparing earlier photos of the length of the needle with/without the nut shows that grinding off perhaps 3/32" off the end of the grip fingers will allow somewhere between sufficient and ample room to allow the needle to seat.

Dan was paying more attention than I was.

[speedytinc]

I won't edit my reply, but looking at your photo again, I absolutely agree with Dan. The fit of the part now is nominally OK and I was quick to judge otherwise. Comparing earlier photos of the length of the needle with/without the nut shows that grinding off perhaps 3/32" off the end of the grip fingers will allow somewhere between sufficient and ample room to allow the needle to seat.

Dan was paying more attention than I was.

The needle is also about of thread. Might take a combination of getting the nut deeper, the friction tabs shortened & even a little counterbore to the top of the nut. Repo parts!

[Hudson29]

First I'll run a tap down the carb body to clean up the threads. There looks to be some paint that may limit the nut from seating as far as it might. Then I'll see if I can grind the ears on the shroud down some. Hopefully, this will provide enough room to allow the needle all the way down.

I do hope whoever made these parts hears of this issue and makes the corrections with the next batch. If I'm having this issue, I'll bet everyone else who buys them is too.

Paul

[speedytinc]

First I'll run a tap down the carb body to clean up the threads. There looks to be some paint that may limit the nut from seating as far as it might. Then I'll see if I can grind the ears on the shroud down some. Hopefully, this will provide enough room to allow the needle all the way down.

I do hope whoever made these parts hears of this issue and makes the corrections with the next batch. If I'm having this issue, I'll bet everyone else who buys them is too.

Paul

I liked Soctt's idea of chasing the nut better. Better to not risk the carb body. Those cuttings will have to be completely removed. They could reach the idle circuit. The body threads were chased before painting. May be a Q-tip with some laq thinner if you must.

[Scott_Conger]

the other problem is that the 1/8 npt thread in the top has a "bottom" to it where it transitions into 1/4-32 and pretty much the only way to open the threads up is to custom grind a tap "short" so as to enlarge the threads. To me, none of this is as palatable as just removing a little bit of the friction fingers. In fact, I'd just bend the damn things open and test fit the needle. Period. I think you're going to find that it fits just fine and a little extra length off of the friction fingers will become self-evident.

My original post about tapping the carb body was as a last resort and requires a custom tap. I have them but don't advise anyone to go grinding up perhaps their only tap.

I test fit an old fitting into 4 original carbs. All seated at varying heights. A new part also fit at varying heights but a little further out.

When it comes to these things, they're sometimes not perfect and one or two guys around here will bellow and curse the mfg for not getting it right. I'd love to be a fly on the wall and watch them make the entire assembly from scratch and see how long it takes them to "get it right".

Think of this as an initiation into the "T" fraternity.

FWIW

[Scott C.]

I had the same problem on a later swivel type. If I remember correctly, what I found comparing the needles was that the new repro later style needle was not threaded far enough up the shaft to allow the needle to hit bottom. I think I still have it some where? I ended up dressing down the original needle point.

[Original Smith]

Keep in mind, the new style adjusting rod was introduced in late 1925. Check out the parts book. There are seven or eight different lengths. I noticed a '25 on the Spokane tour that had one that is about six inches too long! A '25 roadster or touring is 23 1/4".

[Hudson29]

Keep in mind, the new style adjusting rod was introduced in late 1925. Check out the parts book. There are seven or eight different lengths. I noticed a '25 on the Spokane tour that had one that is about six inches too long! A '25 roadster or touring is 23 1/4".

Larry, do you mean the control rod? The nut was the same?

Paul

[Hudson29]

Sunday after reviewing the opinions here and having had a good think about it all, I ran the tap into the carb body. I coated it liberally with oil and it went in easily right up until it bottomed. Wiping several times with a shop rag brought up some grunge but the tap cut no threads and only cleaned a bit of paint out of the top.

I had already run the die on the nut and so I snugged it up into the body. It looks just a bit lower than before:

A trial of the needle showed that it was not yet seated so I ground a portion of the ears away & tried it again:

With the ears still hitting the nut it needed more attention on the grinding wheel so back it went. Several trial fits were made and the last one had the needle hit the seat with clearance between the nut & the needle ears:

This looks like it ought to work so I deburred it & slopped some paint on the ground portions.

There are still other portions of the mixture/primer assembly to sort out before this project is done such as the new sliding part on top of the U-joint which is larger than the old one and the control shaft is now loose inside. It still works but it needs some sort of shimming up to remove the play.

My thanks to all who have shared their opinions & experience. It helped me get things sorted.

[speedytinc]

You could change out the top piece.

[DanTreace]

Paul

Good work there to get the parts to fit, nice massage effort

Playing with these old T's that are nearly 100 years old is more times that needed a bit too much fun (or insert your favorite word)

[Hudson29]

You could change out the top piece.

I would have no problem changing this out for a new one if I could be sure of what I am ordering. The one I have could well be modded or even home made. I'll shoot some pictures of it later today or tomorrow.

[Hudson29]

I have to wonder why Ford changed the nut & needle as they did. Why not just retain the old T bar but with the ends bent up to meet the new U-Joint as the builder on the setup of my car did? It seems that it would have been simpler, cheaper & more effective than the new units. What I an looking at may not work as Ford intended so its hard to judge by what I see. For those of you who have experience with the Ford setup working as it should on the Improved Cars, what did it do better?

Paul

[speedytinc]

The new set up allows for easy in cab carb adjustment compared to your 23 roadster which is difficult to get to on the fly.

[Hudson29]

It is certainly true that I can't reach the mixture control from the driver's seat. My arms aren't long enough . . .

Paul

[Hudson29]

Here is the mixture control rod on my '14:

I do not see anything like it in the supplier's catalogs. I'm guessing it was made for the purpose by the person that installed the carb.

Paul

[Hudson29]

The new needle shaft was loose on the control rod from the dash, looser than I was comfortable with. It needed to be shimmed & I had some sheet brass which would be just what was needed in one of the boxes of modeling supplies hopelessly buried in the great mass of unpacked stuff from the move. AL ought to work, its cheap & on hand. It doesn't have to move or slide much and if kept well greased ought to do the trick.

A soda can was cut with scissors and made into a cylinder which was formed into a square with small screwdrivers inside the shaft. A test fit proved the concept and so a good bead of CA gell glue was used to bond the new spacer to the inside of the needle sleeve. The well greased control rod was worked into the assembly and proved tight enough for Model T standards while still sliding up & down to pull the primer wire.

Working the wire into the primer lever while it was down was a PIA so these little vice grips held the lever in place while the wire was installed & bent.

It all works great & looks neat & tidy if not exactly proper for a 1914.

Paul

[Original Smith]

The priming wire above is not bent the way Ford says to do it. Look in the Service book, and parts books.

[Norman Kling]

Smith,
Which end of which wire are you referring to? Since this arrangement is not original Ford specifications, what difference does it make if it will work?
Norm

[speedytinc]

This carb has the proper early, long choke arms. The 25-26 arms are short & one offset for choke wire clearance, not to mention, the other hardware is made up. There is no "correctness" for this particular set up, only function.

[Hudson29]

I actually bought the correct primer control wire but it was too short to work with this installation. The wire that is on it may be home made. If so, it is well constructed & works well for its purpose. The whole setup is a shade tree combination of various Model T bits with some clever adaptions to make it all work. It does work & very well. Someday it may all go back to Ford standard (as far as this can be determined) but for now I am looking for a good reliable tour car.

Paul