NH Carb Spray Needle Adjustment

[BLB27]

I start my engine with the carb control rod 1 3/4 turns open and then adjust it down until the engine smooths out, which I understand should be about 1/4 turn open. However, the engine runs the best when the control rod no longer turns!

I assume, when the control rod stops turning, the spray needle would be closed and the engine should stop. Am I wrong?

[Allan]

Something weird is going on. I set mine once, and never fiddle with it again. Some like to tinker.

Allan from down under.

[Chris Barker]

'Normal' is about 1 turn from fully clockwise, and the engine will normally stop if you turn the adjuster 1/4 to 1/2 a turn from 'normal'.
be gentle when turning the needle to fully in or you damage the needle faces and jet seat. Maybe they are already damaged and that's why it still runs when fully 'in'.

[bobt]

I concur with Allan down under. bobt

[George House]

I’m at about 1 1/2 turn open from bottoming out. But I learned last week to tighten the pinch nut down snug or it’ll suck air, cause backfire and blow out the outer muffler shell !

[Professor Fate]

If the needle is scored or marred at all, it'll run weirdly or poorly. Cranking it all the way closed, if done harshly, will ruin your needle and maybe the seat too. Be gentle!

[TXGOAT2]

I use the carburetor adjustment as Ford recommended.

[speedytinc]

A picture would help. Common issue with repop 26-7 needles: the friction tabs are too long & dont allow the needle to fully seat.
Your needle is not really only a 1/4 turn off the seat. A proper condition NH wont run @ 1/4 turn off the seat.

[John kuehn]

I have 3 T’s and they all are adjusted around 1 1/2 turn adjustment. You probably noticed the word “around”. One is closer to 1 3/4 than the other two.
For my cars that is what runs best for me.
Fords adjustment is based upon a carburetor in good condition or near new. Over time things begin to wear and owners compensate by readjusting to run the best with what they have.

This comes up from time to time and will again and as parts wear out it’s time for a carb check and needed maintenance.

[George Mills]

All carburetors are different, but these rules and comments generally apply...

The proper 'run' position is somewhere in the 1+ ccw turns...but finding the sweet spot will be on you. CAUTION - engines sound really good when too lean and your only notice is a dull red glow of the manifold at dusk.

I'd almost agree with others, where one universal setting can usually be found, but I have one with a Holly G that will not 'start' at the optimum 'run' position, but open it 1/2 additional turn on starting and no issues. I have that one marked where optimum 'run' is a dot, top-dead-center on the control rod.

I do the walk in perhaps a little different than most, simply because in my early years I had a lot of glowing exhaust manifolds...

I 'open' (G, NH no different) the needle value 1-1/2 turns from a soft close. Start the car and go for a ride. As I drive, I start walking the needle valve closed by 1/8-1/4 turn and wait at each step until I hear the first 'spit' then go CCW 1/8 turn. Not done yet, go for a long drawn out low...and then quickly into high, while raising and lowering the throttle. Any spit of hesitation on the shift, open CCW another 1/8 turn. That seems to do it to find the sweet spot for me probably over a dozen cars by now. When I'm done the 'tweak' I put that black marker dot at 12 o'clock on the knob where there is a knob, and if the Z top rod, mark the position on the dash. Works for me...same spot, start and run a lot of the time. Those that haven't complied, I just open another 1/4-1/2 turn to start, put it back when it starts. Your own experience may differ, works always for me, and no red manifolds.

Another thought is if you run too rich...Model T don't seem mind, but you find out real quick if your eyes don't tell you first...your Miles/Gallon drops into single digits!

[BLB27]

John Karvaly, You pointed out that the friction tabs on 26-27 repop needles are too long and suggested a picture. The attached photo shows that could be my situation, especially if you zoom in on it. I assume grinding the ends of the tabs would correct it, even though that may be difficult.

Thanks! I doubt that I would ever have thought about that situation!

[speedytinc]

Yes it appears that the tabs are hitting the hex. You can trim them or get the brass fitting shorter by one thread. Either thread the brass piece a little more or thread the body a little deeper. 1/8 npt thread. You dont need much, just 1 threads worth.

[Allan]

George mentioned lean running. It is for this reason that I adjust the needle like this. At a reasonable idle, screw the needle down until the engine stumbles because it is too lean. Then back it out again until it stumbles because it is too rich. As you the wind the needle back down again, you are approaching the ideal setting from the rich side, rather than being too lean.

Hope this helps,
Allan from down under.

[Scott_Conger]

Well Hell's Bells

there are more versions of this woeful carb on the Forum Topics than I can keep track of.

Two issues

One: the brass post on top of the carb that screws in - that is a tapered pipe thread and the part is made wrong. The tapered thread is too large in diameter...the hex should be able to run down and either touch or nearly touch the top of the carb. Don't try to tighten it more...it won't go. You will have to buy a split die to run on successive times, each with the die a little smaller, trying to thread the part onto the carb after each time you run the die onto it. When the hex seats against the carb, you're done

Two: the two "fingers" which clamp over the above part usually are too long and crash into the hex before the needle seats. You will need to cut off about 3/32" length of those fingers.

Once the brass fitting is short enough as installed, and the "fingers" can run down further, you should find that you can turn the needle all the way down and gently seat it against the jet in the carb. Thus seated, you can now unscrew 1 1/2 turns, start the car and screw back in until the car runs correctly after it is warmed up.

Now that I posted this, I see others have offered the same advice. Follow anyone's advice and be done with it.

[BLB27]

Here is an update. Steve Lang saw my post and called me. He described my problem the same as Scott did. He offered to modify a brass post and send it to me. He did two modifications. (1) Removed a small amount of thread in the top of the brass post so that the needle will screw further into the post. (2) Used a die to decrease slightly the size if the pipe thread on the bottom of the brass post.

I shortened the friction tabs using a Dremel (see photo).

My problem is solved. Thank you all who responded to my post. A special thanks to Steve. He has also helped me on other items. What great technical resource and representative of Lang's!

[Scott_Conger]

Glad to hear it

this problem is so widespread it is hard to believe that the manufacturer of this part is unaware of the problem or unwilling to make it correctly. I am guessing around 5,000 of them are sitting in a bin somewhere, all made wrong on a commercial screw machine and no one wants to take the time to modify them all. It is a "buyer beware" item.

every one I have ever seen needs to be modified to back to original configuration in order to be used

this is where professional rebuilders who know their stuff and are working for about $5 an hour really earn their keep