Throttle shaft
 

The red book cautions the need to install a new bushing to prevent air leakage if there is wear on the throttle shaft. I can't attach a video, but the free end of this shaft can be moved about 1/16 of an inch--maybe a hair more. Is that enough to cause air leakage of an amount that will affect performance?

Re: Throttle shaft
 

I'll say no, but you could solder the shaft and file to fit if it bothers you.

Re: Throttle shaft
 

Re: Throttle shaft
 

This is a core I am rebuilding. With the shaft inserted all the way the slop is maybe 0.003-0.005" My only fear about a new shaft or new bushing is that the casting will be very hard to hold tight in a drill press, or hold tight in a vise for free-hand drilling.

Re: Throttle shaft
 

Oversized replacement shaft if the bore is enlarged. Sideways not so much, have seen Teflon tape used there. Or try some EZ-turn.

Re: Throttle shaft
 

Why not install the carb and see if it idles OK? - I've come across carbs where there was definitely slop but idled well nevertheless. Solder as Gary WA suggests is one option but if there's an air leak then the oversized shafts mentioned above are available and better than soldering, and they straightforward and easier to fit that trying to rebush

Re: Throttle shaft
 

If you are rebuilding the core then add a new bushing and possibly a new shaft. Why not do the best job you can? To hold it tight in a drill press, you can use hot glue and then peal it off later. One trick is adding masking tape to the part to make removing the hot glue easier. Just peal off the masking tape later.

Re: Throttle shaft
 

In which direction does the shaft move? If it is radially, that will leak and needs to be fixed. If the motion is axially (in/out) 1/16" motion is not likely to be a problem.

Re: Throttle shaft
 

The movement is radially. I was hoping to be able to post a short video so the amount of slop was evident, but can't do it. Will try to add a film of solder --report to follow. The carb I am currently running does not respond at all to changes in the idle air mixture, and I suspect the throttle shaft is the culprit there, also.

Re: Throttle shaft
 

Re: Throttle shaft
 

You are correct. The photo would be of no value if I had slid the shaft all the way in, and I tried to avoid a long essay describing the movement, preferring to post a video. Working on it now--will keep you posted

Re: Throttle shaft
 

Post the video on Youtube then provide a link here to the video.

Re: Throttle shaft
 

Success !! I added a film of solder, filed it down , and it fits with ZERO slop. Thanks for the help.

Re: Throttle shaft
 

For future reference: To hold the body secure in a drill press: Bolt the mounting flange to a piece of angle iron, then bolt the angle iron to the drill press table. Use a piece of 1/4" rod in the drill chuck to align the throttle body. Simples

Re: Throttle shaft
 

Would you add the solder by dipping in a pot, like this?

https://www.fordbarn.com/forum/pictu...ictureid=46724

Re: Throttle shaft
 

I have never been very successful at soldering with an iron, but I have done my own plumbing for 50 yrs. I shined up the shaft with plumber's sandpaper, clamped it gently in a vise, added flux, heated the shaft with a propane torch, and touched some lead-free solder to the target area. Naturally, the solder flowed over the shaft and collected in a bulb on the underside. I quenched the hot item, and used a bastard file to file down the bulb. Am very happy with the result.

Re: Throttle shaft
 

Re: Throttle shaft
 

Reference message #16. I need to to learn how to do this with some old throttle shafts from Simmons Model-A replacement carbs. Thanks for the "how to" Russel Reay!:cool:


Bob-A:D

Re: Throttle shaft
 

Sent you a PM

Re: Throttle shaft
 

I would be afraid to drill it. I can never get the drill angle just exactly correct. Plus drill bits always seem to cut just barely bigger than what the drill size is.

I don't know if I have a reamer that size of not. Pretty small.

I think you made the right choice with the solder. Esp. since it is a spare. You'd be surprised how much slop makes zero difference (that can not be adjusted out) and no one will ever notice.