Is this NH sucking air?

[Steve Jelf]

I'm finally getting around to rebuilding some Holley NH carbs. Today I stuck a new throttle shaft into each one to see if the hole is "wallered out". Checking twelve bodies, I found the hole worn enough for the shaft to wobble in twelve of them. Some wobbled a little, and some wobbled a lot, but all were worn. From this I assume that most of the NH carbs in use have some air leaking in around the throttle shaft. I wonder how seriously these leaks affect performance.

[TXGOAT2]

A loose throttle shaft will affect idle smoothness and stability and may make idle speed erratic. The more wear, the worse the issues. Extreme wear can make idle and low speed operation very erratic. Starting can be affected. Ideally, the throttle shaft fit would be on-spec and the entire linkage would be free of any excess play, and the motor mounts, steering bracket, steering column, body mounts, etc, would be secure.

[Scott_Conger]

Everything Pat posted is true, and is why the price (currently) of a correctly remanufactured NH is such a bargain.

[speedytinc]

The fix is to bore the body throttle holes to fit thin walled brass hobby tubing used as bushings.

[browning]

I have fixed worn shafts in everything from the crankshaft in a Fordson tractor to a 2" diameter planer shaft to carburetor shafts by wrapping the appropriate wire into a pocket turned at the point of wear on the shaft and soft soldering, silver soldering or J.B. welding the wire in place and turning and polishing the repair to the desired diameter. For a worn carb shaft I first measure the diameter of the worn hole in the body, reaming if necessary, and turning the worn section of the old shaft to one wire diameter smaller than the hole. I keep .030 dia. brass wire on hand for the purpose. If the worn hole measures .320 I turn the damaged area to .290 and then drill a 1/32" hole about 1/8" deep at the end of the turned area. With a short bend on the end of the wire and the hole drilled at a little bit of an acute angle the wire can be carefully wound around the turned area, keeping the wraps as tight as possible. I flux the area before the winding, lightly sand the wire to clean it and usually hang a pair of vice grip pliers on the free end when the wrapping is completed. For a brass shaft I use soft solder and gently heat the shaft (careful not to burn off the brass wire) until the voids are filled all around. When the shaft is then turned to the final diameter the wire will be turned to the tangent point of the wire windings and the solder will be all but invisible. Light polishing to provide a sliding fit finishes the process. Using this method allows the repair to be larger than the original shaft diameter only at the carb body and if carefully done is almost impossible to detect. Takes less than hour and costs nothing.

[Mark Gregush]

I have run in all kinds of problems installing brass bushing where there is a brass shaft, such as a throttle shaft, used. I have messed up what should have had plenty of clearance when installing the shaft, with them sticking together. I now use steel bushings which is what is supplied for the Model A carb rebuilds. Not saying that the Model A will fit, just the material I use.

[tdump]

I have not done it to a NH but on some old carbs i have repaired I used a .22 caliber shell for a bushing.

[TXGOAT2]

Brass on brass might tend to gall. Brass shaft; steel bushing, steel shaft; brass bushing.

[JBog]

Forgive my ignorance, but couldn't you just use a good dab of silicone to seal it at the top?

[Alan Long]

The biggest headache I have with thee NH is removing seized main Jets and the Seat of the Needle and Seat assy!
The most recent job I recon those items haven’t been removed since the factory fitted them a century ago!
Alan In Western Australia

[speedytinc]

The biggest headache I have with thee NH is removing seized main Jets and the Seat of the Needle and Seat assy!
The most recent job I recon those items haven’t been removed since the factory fitted them a century ago!
Alan In Western Australia

Blue wrench!
I dont attempt to remove these parts from core carbs without heat.
Its a waste of time & more likely than not going to knacker the slots.

[TXGOAT2]

Silicone will not make an effective repair for a loose throttle shaft. Something like Delrin might make an effective repair if used in place of a steel or brass bushing, but why take a chance? The Model T carburetor is a precision device with closely fitted moving parts that are subject to heat, vibration, dust, corrosion, and lack of lubrication. Makeshift repairs are not likely to give good results, and may make a good repair more difficult to accomplish.

[ABoer]

Alan L .
I don't have any problem to removing main jets and the seats of the neadles .
I heat the NH carb. on the out site with a Acetyleen flame special the surroundings of the main jet and the seat .
After that I throw the carb. in water .
Then T turnout the parts out with a small screwdriver .

I hope it works for you .
Toon

[TXGOAT2]

Pickling vinegar.

[Alan Long]

Thanks Guys.
I’ll have to find some “Blue Gas”
Cheers Alan