From what I gather, hard chrome or not, it seems not uncommon at all for the chrome plating on the shafts to wear through. I've seen a number of them myself. Chrome all worn through and brass showing.

6 hours ago, Namerow said:

As a remedy, replacing or re-chroming the shafts doesn't seem to be an option and (based on what I've read) re-bushing is not a trivial task.  If I had a jeweller's lathe, I suppose I might consider turning down the shaft ends and adding oversized sleeves that I could then turn down to the correct finished OD.

It still seems to me that 240260280's 'fix' -- although as yet unproven -- is worth trying.  Cost = 15 cents per carb.  Time investment (starting with a stripped-down carb) = 20 minutes.  Easy to un-do if it proves ineffective or problematic.  It seems it should absolutely work on the end of the shaft that's flush with the outside face carb body.  It's the effectiveness of the o-ring on the linkage end that's the unknown.

We all know what the other option is... and it starts off at ~ $900.

Building back up with new chrome is a technique used often to repair shafts. But they're expensive shafts that make a $450 replacement seem like a bargain. Big hydraulic cylinders, etc. So yes, that's absolutely a viable technique to fix the wear, but might not be cost effective.

I don't think you want to entertain turning down the shaft ends just for sleeves. Alignment would be very difficult. Would probably be easier to just make a whole new shaft.

As for sealing the vacuum leaks, you're right... Plugging the short end is easy. It's the inboard ends that are more difficult because of the linkage stuff.

My solution is O-rings on the shafts. This pic is for a flat-top I'm working on, but the concept is the same:

According to my limited knowledge but now confirmed by the captain , bushings were steel, shafts were brass, bushings are generally in good condition because the brass is softer and wears first. 

I would have posted up some pics of the shaft wear but my phone decided to $^!# itself completely. 

But some interesting comments have come up which I was not expecting!

@Namerow I actually remember reading @240260280 thread on his solution. But cannot remember if it worked or not. I thought it was clever.

Could one have a machine shop weld in new brass, lathe proud areas to spec then rechrome? Or would it be easier to be completely remanufactured? Seems there should be a bit of market demand for repro throttle shafts? 

Very interesting solution @Captain Obvious so the o rings are within the bushings? So what is the shaft rotating on? The o rings? Would they not wear quickly? Or would regular lubrication do the trick? 

Yes, the O-rings are carefully placed so they run inside the bushings, thereby providing a seal (in theory).

As for what the shaft is contacting while rotating... I haven't done any high level study to actually scientifically determine the contact locations, but my expectation is that there will be still be contact between the shaft and the bushings, but the O-rings will act as sort of a "spring" to center the shaft in the bushing. My belief is that centering spring will do two things:

First, it will reduce the contact pressure (and hence future wear) between the shaft and the bushing, and...
Second, the compliance of the O-ring will provide a seal against vacuum leaks "on the big gap side" even when the shaft is pressed fully to one side inside the bushing.

I lube them when I put them in and haven't had any problems, and while my sample size is small, I haven't had any problems so far. One set has been running trouble free for a couple years now.

Just another technique I sometimes employ in my carb servicing "business".  

Just for the record. ordered and received these eBay SU screw sets. Excellent quality and perfect match for the old screws. If anyone needs new depression chamber or float cover screws don’t hesitate to buy these. 

https://www.ebay.com.au/itm/Datsun-240Z-Float-Bowl-Suction-Chamber-Carburetor-Screws-Set-/164620649300?_trksid=p2349624.m46890.l49292

comparison with old screws, yellow zinc coating looks great

thanks @Zup for finding them and sharing the link! 

Has anyone attempted their own roller bushings similar to what ztherapy manufactures?  I wonder if that’s the solution we need for us guys who don’t need all the bling but want the carbs to perform.  I’d order the ztherapy kit but I’ve heard it’s almost a year backlog!

I haven't seen anyone try it but I've thought about it many times. Surely somewhere in the world someone else is doing it and possibly selling a DIY kit. I've also toyed with a method of sealing worn throttle shafts that uses o-rings secured to the carb housing.

1 hour ago, Mark Maras said:

I've thought about it many times. Surely somewhere in the world someone else is doing it and possibly selling a DIY kit. 

Sounds like something that would be best to come out of Oregon with a jar of jelly. 

I thought C.O. had pursued this also. @Captain Obvious

1 hour ago, Mark Maras said:

I've also toyed with a method of sealing worn throttle shafts that uses o-rings secured to the carb housing.

 

A potential meeting of the minds? I'd buy a ticket to get in on some.

I've done several throttle shafts with O-rings.

@Jarvo2, Have you got any good pics of what ZT does? I've never seen one of their seals.

 

3 hours ago, Mark Maras said:

I've also toyed with a method of sealing worn throttle shafts that uses o-rings secured to the carb housing.

You're not talking about cutting internal O-ring grooves into the (bushing that's pressed into the) carb body, are you? If so, call me and I'll do my best to talk you out of that. 

If that's not what you meant... I've seen a couple simple seal versions. First is on the round tops... The outboard ends can be capped off completely. Only the inboard ends need some sort of rotational seal.

And someone many moons ago did a simple "crushed O-ring" compressed up against the outside of the carb body. (@Blue @240260280 maybe)