HS6 v 175CD

[GarethC]

Hello everyone,

This is my first post on this forum so please bear with me.

I have tried to search under SU HS6 but the search engine will not permit this so apologies if this has been covered before.

I have just purchased a TR4 which is fitted with Stromberg CD175 carburettors and is running rich, having had a play trying to get them to run a little leaner I think they are due a rebuild.

Now the point of this post is that I have some TR7 HS6 carbs available and was wondering if reconditioning and fitting these would be a better option.

Would I have to buy adapter plates and if so, why?

What linkages would I require and are there any other issues that I would need to consider?

 

Gareth.

[67_gt6]

Hi Gareth

 

I can't advise on the specifics of the swap over but I can point out the following advantages of doing it: -

 

wider range of needles available

no rubber diaphragms to worry about

needle valves less prone to sticking open (in my experience)

setting float heights and all the rest of it no where near as much of a b*ll ache as it is with Strombergs where the bowls are underneath the carb

 

Andy

[randall977]

Most importantly - they look nicer.

[Smokey]

I've used both SUs and Strombergs, and I guess I don't understand some of the negative views on the latter. My 1965 TR4 had Strombergs, and I drove that for five years with no problems in the late '60s. You just have to adjust the mixture for the seasons, and that's much easier on the 175CDs than on SUs - you can just use a coin. I rebuilt the Strombergs on my TR250, and it was quite easy - just follow the instructions in the TR250/TR6 workshop manual - a couple of evenings work. Admittedly, I did not rebush them, which would require a machine shop. Long story short - I like Strombergs, and have had very good experience with them. My advice - rebuild the 175CDs and keep it original.

[John Morrison]

I concour fully with Smokey.

 

Fitted Strombergs to my 1963 Tr4 after it came with SU's. My car was original on Strombergs, twelve years later no probs at all, dead simple, and although I carry spare diaphragms, never in all that time had a problem.

 

Certainly if your car is standard spec or nearly standard would not hesitate to stay with what you have.

 

john.

[GarethC]

Thanks everyone,

 

The car is standard, still on dynamo and positive earth so maybe I should endeavour to keep it as Mr Triumph intended (for better or worse)!

 

Regards,

 

Gareth.

[Alec Pringle]

Hi Gareth,

 

Strombergs get a bad press, often enough from folks who don't actually have any personal experience of them. I've never had problems with Strombergs, and I've driven quite a variety of cars, not just TRs, so equipped since the late 1960s. To be fair, SUs are the better bet for a tuned engine - Strombergs are not as versatile, and they won't work as well in competition. But if you're driving a standard(ish) car, they should do the job perfectly well.

 

Cheers,

 

Alec

[Smokey]

If I recall correctly, Kastner's Competition Manual describes a simple procedure for fitting SU needles into Strombergs for tuning. It requires a small semi-cylindrical shim to allow for the larger hole in the Stromberg piston. Strombergs were mandatory for racing a TR6 in SCCA, if I recall. So tuning Strombergs is quite easy, and from an engineering point of view, the diaphragm is an elegant way of maintaining vacuum - no need to worry about wear on the piston. Replacing the diaphragm takes about five minutes.

[Smokey]

By happenstance, I just received the original TR4-TR4A Competition Preparation Manual I bought off ebay, and I thought I'd share Kas Kastner's opinion about Strombergs . "The diaphragm gives a more accurate air depression and raising of the piston than the SU.." The procedure for using SU needles is in the attachment. STROMBERGS RULE!!!!

Kastner re Strombergs (2).pdf

Kastner re Strombergs (2).pdf

[Alec Pringle]

Hi Smokey,

 

over the years I've gained the impression that the good Mr Kastner was always a pragmatist, who made the most of what options were available to him, and didn't waste brainpower on those that weren't. Here in the UK the options of SU or Stromberg have usually been open, and if Strombergs had offered any ultimate advantage that would have been exploited. I'd suggest it's fair to assert that in terms of competition TR engines SUs would be the preferred option over Strombergs, unless of course the regs dictate otherwise . . . .

 

So no, I rather doubt that Strombergs do, or ever could, rule in competition - other things being equal. However, in an average road configuration, they'll work just fine.

 

Cheers,

 

Alec

[Ade-TR4]

Couldn't sleep, Alec?

 

I would get the Strommies rebuilt as opposed to using TR7 HS6s.

The later HS6s have extra pipework on the body that needs to be blanked-off.

 

I've a set of TR4a HS6s if you desperately want some. But I'd stick with original if the rest of the car is standard or very close to.

 

Cheers

Adey

PS: Andrew Turner will recon the Strommies and does a VERY nice job too.

[GarethC]

Once again thank you for all your advice.

 

I have e-mailed Andrew Turner and he has also been very helpful.

My only concern is that because I am not clued up on Strombergs how do I ascertain if a rebuild is actually required? Maybe I should just bite the bullet and get them reconditioned so at least I will then be sure that all is well with them.

 

Gareth.

[Smokey]

Gareth, the only reason I rebuilt the Stombergs on my TR250 is that they were leaking fuel from the various seals and gaskets. However, if there is any doubt, it's probably better to get a good rebuild so that you have a solid baseline.