TR4/4A 67 carbs

[TFB]

I am looking at a 1967 tr4a IRS that is unrestored in nice all original condition.I restored my TR3 so pretty familiar with the basics,but the carbs are SU's,with a center pull linkage.
I thought Zienth Stombergs would be the right cabs for this car,but everything else is so untouched I am not sure.Any info appreciated.
Thanks
Tom

 

[glemon]

The switched back and forth over the production run. I am not sure if anyone has a clear record of when they switched back and forth, generally speaking, either carb is fine for a Four A.

 

[Geo Hahn]

I am looking at a 1967 tr4a IRS... the carbs are SU's,with a center pull linkage.

Sounds right to me. An unrestored original is a good find.

 

[charleyf]

Tom,
Because I bought an early to mid production( 17000) TR4 with ZS carbs on it,I decided to do some research. What I found is that there was a period in the mid production that they put 1000 ZS carbs on the cars. Then They went back to the SU's for a time. Then ultimately switched to the ZS for good. The primary reason for the original switch was lack of production from SU as I understand it. The ZS carb was designed and built to serve the same function ( possibly by folks at Standard TRiumph) during this period of lack of adequate production by SU.
If you have the center pull linkage then what you likely have is the HS6 carbs with the AUC209. I personally view these carbs as superior to the H6 SU that came on the earlier TR4's. I have just rebuilt two sets of these and put them on my TR4s. I have never dealt with or used a ZS carb so I am biased. But you do likely have an original setup. A local friend has the same set of 209's on his TR4A. I would add that the linkage mounting piece that mounts below the carbs is really hard to find. The carbs themselves are getting rare as well.
Charley

 

[TR3driver]

FWIW, the story I've heard is that SU became part of BMC, which was Triumph's competitor at the time. Supposedly Triumph was paying twice as much for SU carbs as MG was! (along with being more affected by strikes, lack of production and so on). So the ZS carbs were to cut costs and get better control of their own destiny. But then when BMC fell on hard times, they got effectively taken over by the UK government, who applied pressure to Triumph to go back to buying SU carbs. (And shortly afterwards, the two companies merged anyway to become British Leyland.)

Piggott gives the change point (to the SU HS6 carbs) as CT62191. But I suspect that is approximate, since the SPC just has a blank.

IMO the HS6 is definitely a superior design to the H6. The float bowl mounting seals and cork jet seals, which are perennial fuel leakage points on the H6, were both eliminated. The center pull linkage reduces the force on the front throttle shaft bushing, greatly reducing wear at that point. And according to several people (including Kas Kastner), they even flow better! I've got a set on the shelf myself (but decided to stick with the original H6 carbs for now).

The SU patents got transferred to Burlen Fuel Systems, who I believe still make complete HS6 carbs. https://burlen.co.uk/

These folks https://www.ztherapy.com/products/SUReman.htm can even install roller bearings and seals on the HS6 throttle shafts. They cater mostly to the vintage Z car crowd, but can do the same for genuine SU carbs as well. (240Z et al used an almost identical Hitachi clone of the HS6.)

 

[TFB]

FWIW, the story I've heard is that SU became part of BMC, which was Triumph's competitor at the time. Supposedly Triumph was paying twice as much for SU carbs as MG was! (along with being more affected by strikes, lack of production and so on). So the ZS carbs were to cut costs and get better control of their own destiny. But then when BMC fell on hard times, they got effectively taken over by the UK government, who applied pressure to Triumph to go back to buying SU carbs. (And shortly afterwards, the two companies merged anyway to become British Leyland.)

Piggott gives the change point (to the SU HS6 carbs) as CT62191. But I suspect that is approximate, since the SPC just has a blank.

IMO the HS6 is definitely a superior design to the H6. The float bowl mounting seals and cork jet seals, which are perennial fuel leakage points on the H6, were both eliminated. The center pull linkage reduces the force on the front throttle shaft bushing, greatly reducing wear at that point. And according to several people (including Kas Kastner), they even flow better! I've got a set on the shelf myself (but decided to stick with the original H6 carbs for now).

The SU patents got transferred to Burlen Fuel Systems, who I believe still make complete HS6 carbs. https://burlen.co.uk/

These folks https://www.ztherapy.com/products/SUReman.htm can even install roller bearings and seals on the HS6 throttle shafts. They cater mostly to the vintage Z car crowd, but can do the same for genuine SU carbs as well. (240Z et al used an almost identical Hitachi clone of the HS6.)

Thanks every one for all the replies and info.I had a pretty original 64tr4 back in 1970with the ZS carbs so I thought everything after that was ZS.I forgot about the hs6.
The center pull set up looked like it would be a nice upgrade for a tr3.
Thanks again
Tom

 

[sail]

That unrestored, in nice original condition caught my eye.

 

[charleyf]

Tom,. I would add that the linkage mounting piece that mounts below the carbs is really hard to find. The carbs themselves are getting rare as well.
Charley

UPDATE-- I was just looking at a T R Shop ( of London) ad and saw that they have the full linkage package for sale. Not cheap but it is available. Another note is that the newer SU carbs that you can now buy appear to have a newer needle set up/ the newer needles have a spring at the top and no longer have to be centralized into the jet. I suspect it makes it easier but it might wear the needle faster.
Charley