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mikeh

Strombergs - throttle spindle bushes

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Last year, I rebuilt the Strombergs on my 4 and, after some faffing around with float levels, got them running a lot better than they had been previously.

However, the one issue which I was unable to tackle was that of leakage around the throttle spindles and I've now concluded that this is why I’m struggling to get a decent idle. There's no wear on the shaft - it’s actually the carb body which is worn as there was no bush fitted originally and the spindle simply runs in a bare hole in the casting. It’s difficult to measure the wear but, using a dial gauge, I reckon there’s about 5 thou (imperial) of play.

As I’d like to stick with the Strombergs, I’m looking for someone who can make/supply/fit suitable bushes to deal with the problem. Unfortunately, the spindle size is not the same as on SU’s so, while I’ve found quite a few suppliers offer a re-bushing service for these, they’re not able to do the same for Strombergs.

Any suggestions of suitable suppliers would be appreciated, even better if they’re in the Midlands!

Thanks

Mike

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33 minutes ago, mikeh said:

Last year, I rebuilt the Strombergs on my 4 and, after some faffing around with float levels, got them running a lot better than they had been previously.

 

However, the one issue which I was unable to tackle was that of leakage around the throttle spindles and I've now concluded that this is why I’m struggling to get a decent idle. There's no wear on the shaft - it’s actually the carb body which is worn as there was no bush fitted originally and the spindle simply runs in a bare hole in the casting. It’s difficult to measure the wear but, using a dial gauge, I reckon there’s about 5 thou (imperial) of play.

 

As I’d like to stick with the Strombergs, I’m looking for someone who can make/supply/fit suitable bushes to deal with the problem. Unfortunately, the spindle size is not the same as on SU’s so, while I’ve found quite a few suppliers offer a re-bushing service for these, they’re not able to do the same for Strombergs.

 

Any suggestions of suitable suppliers would be appreciated, even better if they’re in the Midlands!

 

Thanks

 

Mike

 

Hi Mike

I believe they do have a replaceable throttle spindle and bush. Item 55 in this link from Moss. It is likely you'll get rough idle if the bush or shaft is worn.

https://www.moss-europe.co.uk/carburettors-air-cleaners-175cd-zenith-stromberg-tr2-4a.html

Regards

Kevin

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Hi Kevin,

Thanks very much for that - I hadn't spotted that Moss actually do a bush for repairing the worn carb body. I think these are probably designed for SU carbs as they're for a 5/16" throttle spindle whereas the Stromberg is 8mm but, as there's only a few thou difference, there should be enough wall thickness to allow them to be reamed to suit.

That's a great start so I now need to find someone who can do the machining work necessary to fit them - any suggestions gratefully received!

Regards

Mike

 

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Hi Mike,

I have done some conversions on Strombergs. The easiest way, without machining, is to use the rollers bearings as suggested by Jochem. On a TR6, at the ends of the spindle, you will find a seal. Usually these are hardened over the years and no use at all. The roller bearing fits exactly in the space where the the seal sits. Use a thin coat of loctite on the outside and the inside of the bearing.

 

On idle the throttle valves are closed and there is a high vacuum in the throttle body. Even little play at the spindle or at the outside of the valves will result in air leaks and an rpm too high for idling.

 

As to 8mm bushes: the difference between 5/16 inch and 8 mm is 0,06 mm, which is far too much for a fit on a spindle and a bush. The machining of the throttle body will be expensive, because you need a jig for positioning. I have done some conversions on PI throttle bodies, this is no problem if you use a dedicated jig.

 

Regards, Peter.

Edited by peterq

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Hi Peter & Jochem,

Thanks for your replies. The early CD175 carbs, as fitted to the TR4/4A, don't have the spindle seals you describe, so, although the bearing sounds a very neat & easy solution for the later carb design, unfortunately it doesn't work in the same way on the earlier one.

As the spindles run directly in the carb body and it's the body which is worn, there doesn't look to be any alternative to machining the body and installing a bush/bearing of some type. Oversize spindles are available for SU carbs but seemingly not for Strombergs.

I'm therefore looking for a supplier who can do the necessary machining & fitting work and has some experience with this.

Thanks again

Mike

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1598496413_ManifoldinLathe01.jpg.a319208f8115e1b8902ef8eac6255d34.jpg

Manifold in lathe to drill for the bearing

1783845398_manifold01.jpg.b326b6f301bf51bbd2bfb08fe1218446.jpg

ready to accept the bearing

 

1100220129_manifold03.jpg.b149f18a01fd0cd901854ffc9071caca.jpg

and bearing in place

 

770480351_Spindledriller01.jpg.2abe2433c60ac03080cd62f65b076f24.jpg

my homemade tool

 

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It is easy enough to open up the ID a few thousandths by lightly chucking the bush in a lathe and using emery cloth wrapped around a small stick or rod. But you still have to deal with machining the carb body to accept the bushing. Easier and more economical to trust the job to a carb rebuilder. I am sure there must be several in the UK.

Berry

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Hi Berry,

Yes, it's definitely not a job for which I have either the kit or the skills, but there are quite a few carb rebuilders around. The challenge has been finding one who will a) deal with Strombergs (a number of them won't) and b) will do the re-bushing on its own without it being part of a full rebuild.

I've now got a couple of promising leads so hopefully will get it sorted.

Regards

Mike

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Just to update this thread ................. I did eventually find someone to supply/fit the required throttle spindle bushes. Most of the usual suspects either wouldn't touch Strombergs or would only do the work as part of a complete overhaul/refurbishment. However, both Southern Carbs (as recommended by Stuart) and G.W.Carbs would fit bushes to a stripped-down body, which is what I wanted. I opted for Glen Watson at G.W.Carbs - despite his web address (www.sucarbs.co.uk) he does deal with other types too. He did an excellent job quickly and at a very reasonable cost. (Usual disclaimers, etc. I'm just a satisfied customer)

For other reasons, it's taken a while to get the car back on the road, but the end result has been very satisfactory. While one would probably never call a 4-pot TR idle 'smooth', it's a lot smoother than before and pulling away from rest is more progressive too, especially when cold. I didn't think the play was really excessive at c5 thou, but was clearly wrong as sorting it out has made a big difference.

If anyone wants any more details then just let me know.

Regards

Mike

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