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damper unscrewing


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Hi everyone

the dampers on my SU carburettors are prone to unscrew. No way to eliminate the problem: you can screw them as tight as you can ...they unscrew! I even tried to block them with tape: better but not reliable, as tape gets soft with engine heat and after a while it becomes uneffective. I am thinking of making a little hole in the black plastic top of the two dampers and to connect them with a small rod.

Any suggestion?

Thanks

Alberto

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Thanks Kevin,

probably worn plastic threads is the answer, even if they do not look bad.

I am reluctant to change the dampers but I am afraid their end has arrived...

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Some race cars running SU's wire lock the damper tops but that is assuming the older brass caps rather than the plastic probably.

Having said that I believe I have seen a racing Cooper S with plastic caps wire locked. I have the older brass caps which I tighten by hand & then give a tiny tweak with a spanner to 'lock on'. Seems to keep them tight.

Cheers.

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Some race cars running SU's wire lock the damper tops but that is assuming the older brass caps rather than the plastic probably.

Having said that I believe I have seen a racing Cooper S with plastic caps wire locked. I have the older brass caps which I tighten by hand & then give a tiny tweak with a spanner to 'lock on'. Seems to keep them tight.

Cheers.

Yes you can probably get a bit more bite on the brass type Monty. I've never seen them wired, but don't doubt some racing Cooper S's for example might want to do that. I worked at a BL dealer for quite a few years but don't remember any coming undone, let alone both.

 

Kevin

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I've never really given this much thought.... I have always just nipped them to ensure they are tight each week along with usual checks - the only set of SU's that havn't moved much are the current ones on my 4..... took the same approach with stroms as well.

..... Andy

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I think that to wire lock the tops is an interesting option.

I have run my TR4A for 100.000 miles without experiencing this but once they started to unscrew, the problem got worse and worse.

Edited by mcgrison
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Metro Turbo had this issue. The clamp they fitted stopped the damper falling out did not lock it from unscrewing.

http://ebayapi.loc8apartltd.netdna-cdn.com/00/s/MTA5M1g3NjU=/z/F7EAAOSwe7BWx2lz/$_1.JPG

 

Peter W

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Just make sure you haven't put a chrome sleeve over your carbs to make them look better - I did that on my Morris once; it seemed fine but consistent slight pressure from the sleeve on the cap always saw it unscrewed after a week.

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Thanks Ron. You are right. I put the chrome sleeves over the carbs many years ago. I had to shorten their neck with the file , to prevent what you say and untill last month they did not cause any trouble. I just checked them right now and they do not touch the damper top but are very near. I will shorten them a bit more and let you know.

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Alberto I also have the same problem but with only 1 of them I switched them around and the problem followed,I had a good look at the Threads and they look good but obviously one isn't,they are available New fron Burlen Carbs.

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Very interesting Niall! As I wrote above, this afternoon I filed the necks of the chrome sleeves, in order to reduce their high of 5 mm. and to be sure they do not interfere with the plastic top of the dampers. After that, I drove the car for 40 miles and they did'nt unscrew. Cross fingers!

One question: do you have the chrome sleeves as well?

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On 6/18/2017 at 10:47 PM, mcgrison said:

Very interesting Niall! As I wrote above, this afternoon I filed the necks of the chrome sleeves, in order to reduce their high of 5 mm. and to be sure they do not interfere with the plastic top of the dampers. After that, I drove the car for 40 miles and they did'nt unscrew. Cross fingers!

One question: do you have the chrome sleeves as well?

No Chrome Sleeves,what I do at the moment to keep it in place is wrap it with Insulating Tape and don't block the Breather Hole.

 

Edited by TR NIALL
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Hi Alberto,

 

You could try “Heat shrink” tubing to fit over the SU neck and up a bit over the screw cap. You can get it in quite large diameters, and probably not go soft with the engine heat, which tape will probably do.

 

I see you are in Maggiore. Can't think of a more perfect place to drive a TR. (Lucky B.)

 

Charlie D

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post-835-0-75984100-1497894323_thumb.jpgHi Charlie,

heat shrink tube could be a good solution! For the moment , after I shortened the chrome sleeves necks they are not unscrewing any more but I must try on a longer distance. Next week I'll go with my wife to Isola d' Elba on the TR ( a journey of 600/700 miles) and we'll see.

Anyway, to be sure, I prepared the two plastic caps to be connected with a small rod ( see the attached pic).

And yes....Lago Maggiore is a good place to drive a TR but Herefordshire as well !!

Edited by mcgrison
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attachicon.giflegamento carburatori TR4.JPGHi Charlie,

heat shrink tube could be a good solution! For the moment , after I shortened the chrome sleeves necks they are not unscrewing any more but I must try on a longer distance. Next week I'll go with my wife to Isola d' Elba on the TR ( a journey of 600/700 miles) and we'll see.

Anyway, to be sure, I prepared the two plastic caps to be connected with a small rod ( see the attached pic).

And yes....Lago Maggiore is a good place to drive a TR but Herefordshire as well !!

 

 

Don't block the breather holes in the damper plastic caps. They are required to make the carb work correctly.

 

Peter W

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exactly: two new holes 2,5 mm of diameter...but for the moment I keep the rod in the glovebox. The day the caps unscrew again....I 'm ready!

Edited by mcgrison
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  • 3 weeks later...

Hello everyone, the friends of dampers!

I am just back from a 850 miles journey to Isola d'Elba-Tuscany on my TR4A. Fantastic sea, hotel, sun, food, ecc.

Here is un update to this topic. I discovered that my dampers do not unscrew: they pop up directly, as thread is worn. For this reason, the device I had invented ( the little rod I had fitted to the black plastic screw) does not work.

To block them I returned to the insulating tape : until now this is the only real solution ( not very elegant but effective).

At this point...I will buy new dampers!

Edited by mcgrison
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