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MG TD TF 1500 - New H carb spindles with O ring

One of the chaps on the Morris Minor forum discovered new modified throttle spindles with an O-ring being offered for HS2 carburettors. Further research shows that the same is being offered for the H type. This could be in our interest.
http://www.ebay.co.uk/itm/SU-CARB-H-type-NEW-throttle-shafts-Suit-Austin-Healey-Rover-Jaguar-Triumph-etc-/361864023069?hash=item5440c6cc1d:g:ADsAAOSwqu9VAZTc
He mentions H4 ... H8 but I'm sure he would be able to offer the same for the H2.
I have contacted the seller to find out and will post back when I hear from him.

Regards
Declan
D Burns

Declan,

This is perfect timing for me as I have worn spindles on both my carbs. I have checked in my scrap parts bin and can confirm that the H4 and H2 shafts are the same diameter and have the same hole spacing. The only question I have is how long will the O rings last.

John
J Scragg

John,
That's the 100$ question! I would rather see a lip seal for such an application.


I just got a reply from him:


quote
"Hi thanks for the enquiry. Yes the shafts for a MG TD are £23 each (delivered to a UK Address).

Bill "
unquote


Regards
Declan
D Burns

I had new shafts put in mine during a rebuild. The lip seals might be a quick fix, but I don't care for the 0 ring setup. Is that 23 pounds for each spindle or a pair? If the shafts are loose, they should be replaced with proper fitting new ones. Rebuild the carbs and do it right. JMHO. PJ
Paul Jennings

Declan

I dont believe this is an application for a lip seal, they are usually fitted where longitudinal travel is involved, as found in hydraulic and pneumatic cylinders. If you where taking the design enhancement to the end degree you would fit lip seals at the shaft extremities installed in the carburetor bodies to prevent dust and dirt intrusion.

Machining of O ring grooves requires a little research as there are distinct dimension differences between dynamic and static applications. As this is a rotating shaft application I hope the supplier has done his homework.

I believe this is rather clever, metal to metal seals where a vacuum is involved is difficult to maintain as the number of carburetor rebuilds attests.
G Evans

I think that lip seals at the shaft extremities are the proper way to do it - an O ring arrangement in the way employed here, is a poor solution.
Dave H
Dave Hill

George,
I have to disagree. They are not just for longitudinal travel. They are commonly fitted on rotating shafts e.g. crankshafts.

Paul,
As mentioned above it states £23 each

Regards
Declan
D Burns

I'm not a fan of this method. The o-ring would have to never expand or contract, and be an extremely precise fit to offer no resistance yet still seal. With much resistance added, you would have to use stronger return springs and that wears out the bushings faster.

There is a rebuilder out here who uses a non-metallic throttle shaft bushing that last much longer and seal better than the standard metal ones. I don't know what the material is, but it's blue-ish in color. I have them in my TC carbs and after many years they are still leak free.

It I were going to use a rubber seal, I think I'd prefer if to sit outboard so the tension could be controlled, and seal replaced if needed.
Steve Simmons

Probably Acetal or Polyamide - maybe oil filled, is my guess. Sounds like an interesting idea. Could be an inclination to stiffen up slightly when warm, but depends on the fit I suppose.
Dave H
Dave Hill

Haven't had any such issues, but I don't know his sizing and fitting method.
Steve Simmons

If he's made plenty there is good chance all those issues have been avoided. It would be interesting to find out what the material was.
Dave H
Dave Hill

The idea is quite old. In my (single) H2 the pictured solution is fitted.

The bushes are a sort of fiberish material and must have been fitted in the 1960's. It's leak free and has no play.

A clever solution, that is a several notches above makeshift?

Willem van der Veer

The SU HD6 carbs on my Jaguar 3.8S have a sort of seal on each end of the throttle shafts which is called out in the WSM as a throttle spindle gland which is held in place with a cupped washer, a spring, and a shroud for the spring. All this is shown in an expanded view of this area of the carb in the WSM but strangely does not show in the parts manual. Perhaps SU fitted these to the larger carbs but not to our smaller ones. I wonder if they could be retro fitted to smaller carbs? They seem to work pretty well as these carbs have never been apart in 160,000 miles.
John Quilter

Thanks, I looked up the HD6 on the Burlen website. There are four parts to it - spring, cup washer, annular cork gasket, cap. It looks like it may fit into a recess cavity on the carb body, but I am not entirely sure. Not doubt the spring loads the cork to maintain the seal. More similar to an O ring than anything else, but has the advantage that it is / they are positioned outside of the carb bushes. One of the several issues with putting O rings on the spindle is that they won't work when the bush (es) wear oval.
Dave H
Dave Hill

I have been using PEEK bushings for the throttle spindles. Along the line of Delrin, but PEEK is better. The o-ring thing has been tried many times before. Probably easier to do just it right.
D mckellar

This thread was discussed between 15/02/2017 and 22/02/2017

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