Jump to content

IGNORED

SU fasteners suppliers/throttle shaft?


Recommended Posts

Hi all

Wondering if any of you gurus can direct me to a fastener supplier that would have oem equivalent fasteners for my SU rebuild? 

For example the PO had stripped all the dome screws, I ruined the bowl drain plug and float lid screws on one float bowl. I ruined the throttle flap screws on one SU.

Also struggling to find somewhere that supplies new throttle shafts, mine are worn into the brass. 

And before anyone says ask the guys at ztherapy, I did and they said they don't supply fasteners. Didn't ask them about the throttle shafts. 

Ryan 

Edited by 240ZBUILTBYME
Link to post
Share on other sites

There are lots of good suppliers for metric fasteners.  I've used Bel-metric (located in Massachusetts) and was happy with product, service and prices.  They can also supply the braided hose that you may want for your cooling and emissions systems and your fuel tank hoses. 

www.belmetric.com

https://www.belmetric.com/metric-screws-c-10/?zenid=hoahf6ge7erqkui8k2t7udijt3

Not sure that you'll be able to get everything you want for your carbs, though.  I wonder if it would be a good idea for you to also pick up a set of old Hitachi-SU's that you can rob parts from.

I seem to recall running across someone who sells throttle shafts separately.  Might be Z-Therapy.

  • Like 1
Link to post
Share on other sites
5 hours ago, 240ZBUILTBYME said:

For example the PO had stripped all the dome screws,

Thats because these screws are NOT Phillips #2  they are JIS.. a Japanese type of screw recognizable  by the little dot near the cross on the head!

However you can use a phillips screwdriver if you are a bit careful..  Before turning check fitment and sometimes first a tap with a hammer on your screwdriver will also help unscrew.

  • Like 2
Link to post
Share on other sites

Is it the shafts that are worn, or the brass bushing? I ask as the shafts are steel (hard) while the bearing is brass and softer. Have you measured the shaft dia against somewhere else on the shaft that isn't in contact with anything to wear the dia down to gather what dia has been lost? Just trying to see what is going on.

Link to post
Share on other sites
11 hours ago, Namerow said:

Not sure that you'll be able to get everything you want for your carbs, though.  I wonder if it would be a good idea for you to also pick up a set of old Hitachi-SU's that you can rob parts from.

Thanks for the recommendation namerow! Yes it would be great to have another set! But unfortunately west Australia has very few z's so spare Su's are hard to come by.

Edited by 240ZBUILTBYME
Link to post
Share on other sites
10 hours ago, RIP260Z said:

Is it the shafts that are worn, or the brass bushing? I ask as the shafts are steel (hard) while the bearing is brass and softer. Have you measured the shaft dia against somewhere else on the shaft that isn't in contact with anything to wear the dia down to gather what dia has been lost? Just trying to see what is going on.

No the shafts aren't steel, they're chrome plated brass. Bushings look to be in good condition. As per z therapys spotters guide all their throttle shafts they pull out of old su's are worn into the brass exactly as mine are. 

I will however take some measurements out of interest 

 

Link to post
Share on other sites
On 2/15/2021 at 2:14 AM, 240ZBUILTBYME said:

Also struggling to find somewhere that supplies new throttle shafts, mine are worn into the brass. 

Don't forget that it may not be just the shafts that wear. The bushes may get 'ovaled' because of the suction load (enormous ) put on on the throttle plates when the engine is operating at closed-to-part-throttle.  I suspect that Z-Therapy decided on using roller bearing replacements not just because of the lower friction, but also because it allows them to re-use the old throttle shafts without having to worry about the worn-out friction surfaces.

I'm not optimistic about your chances of finding NOS replacements.  I suspect that whatever was out there was scooped up by racers and carb rebuilders long ago.  For that reason, you may be forced to re-use your old throttle shafts.  If you do, I don't think you need to worry about excessive friction caused by the worn-off chrome plating on the shaft ends (although they're going to wear even faster now that the hard chrome surface is gone).  The real problem is going to be air leakage into the carb body because of the excessive clearances between the shaft ends and the bushings.  

Years ago, CZCC member, @240260280 (aka Mr. Hoover) wrote an interesting article on the old AtlanticZ website about his attempts to solve the air leak problem by sealing off the exposed ends of throttle shafts on the outside of the carb body.  He glued a small plastic cap over bushing boss on the 'flat' side. On the other side, where the shaft extends out of the carb body, he installed an O-ring that was pushed up against the side of the bushing boss (and where -- theoretically -- the suction from inside the carb would pull the O-ring up tight against the surface of the carb body to create a good seal).  Maybe Phil will offer some comments here about how that worked out.  From what I can see, capping the flat end is easy and should be 100% effective at sealing off that end.  The effectiveness of the O-ring on the other side is debatable, and there's also the possibility of binding.  Nevertheless, the overall approach seems cheap and painless to implement and it could reduce the air leakage problem by ~ 75%.

Edited by Namerow
Corrected my mistake re type of shaft bushing material.
  • Like 1
Link to post
Share on other sites

All of the bushings I've seen in the Hitachi carbs are steel. I've never seen one made from brass or bronze. For you guys saying the bushings are brass or bronze (@RIP260Z and @Namerow), Have you seen brass or bronze bushings with your own two eyes? Have you used a magnet to verify?

Also, I've never seen a steel throttle shaft. Everything I've seen are coated brass. Early ones are chrome plated and later ones are low friction greenish coating, but they're all made from brass underneath. Again, can anyone confirm that they have really really seen steel shafts? Got any pics?

Link to post
Share on other sites

You're absolutely right, CO.  I just put a magnet up against the bush in one of my spare carb bodies and it is, indeed, steel.  Who knew?  I would never have expected to see a chrome-on-steel friction surface, but there it is.  I guess the designers already knew about the high loads and decided that oilites wouldn't hold up.  As for misidentifying the shaft material -- I didn't do that.

So: Based on my brand-new knowledge, I have no idea whether those steel bushes suffer from much in the way of wear compared to that experienced by the shaft ends.  The basic problem of wear-generated air leak-past remains.  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.

Link to post
Share on other sites

Hard chrome is frequently used on steel shafts, rollers, cylinders, etc. I doubt you'll see much wear, if any, on hard chromed butterfly shafts. In the past I've found oil lite bushings to be very durable as long as they are oiled regularly.

Link to post
Share on other sites
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:
P1180160.JPG

  • Like 1
Link to post
Share on other sites

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? 

Link to post
Share on other sites

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".   LOL

Link to post
Share on other sites
  • 1 month later...

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

956E9CA4-DB4D-4169-A3BD-DCE41AD331DE.jpeg

BD60E56B-16E4-4719-AE86-4A216E842A3A.jpeg

thanks @Zup for finding them and sharing the link! 

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.