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S.U. carb identification

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Alan_Myers

Alan_Myers

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Hi all, Can someone advise how to positively tell H6 and HS6 carbs apart from each other? I've got a set that I'm not sure about. One possible clue is they are mounted on a TR4A manifold, but this was originally on my '62 TR4 so it may or may not mean anything. Thanks in advance!
 
Alan, the HS6 has a tube running from the bottom of the fuel bowl with the plastic jet tube going up into the center for the needle. H6 bowl attaches with a bolt and the jet assembly is a separate bunch of little parts, painful little buggers. Wayne
 
Hi Wayne,

Thanks for the info! Based on what you've said and some more research I've been doing, I'm pretty sure these are HS6 carbs, but they don't look like the ones in the Victoria British catalog. Yes, they have the float bowl attached on the side and the enrichment (I think) fuel supply tube coming from the bottom of the float bowl, leading over to the jet tube. However, the ones at VB are listed as having 2 dashpot screws per carb, mine have 4 per carb. Also, the bottom of the float bowl shown at VB is "notched", with that fuel line coming out of the lower part sideways. Mine have squared off bottoms on float bowls and the fuel line exits straight down. Also, the jet adjuster on the VB HS6 appears to be a hex nut that would require a wrench. Mine have a knurled ring that allows adjustment by hand. Maybe there are different types of HS6s?

While we're on the subject, has anyone seen HS8s (2") used on a performance TR engine?

Thanks again!
 
Hello Alan,
those sound rather unusual, is there a small metal plate attached to one of the float chamber screws with a reference number? If you can quote that I may be able to identify them. There are Japanese carburettors made (I forget the name) that look very like S.U.'s and were used on the Nissan 240, 260Z etc series of cars, could that be what they are?

Alec
 
Hi Alec, I tried to reply earlier. Guess it's a newbie thing it never showed up.

No, there is no tag or any identifying marks on the carbs that I can find, at least on the exterior.

Yes, I am aware of both SUs and SU-copies on some of the Z cars. In fact, these do look quite similar to a set I saw in a photo on eBay recently. However, it wasn't a large photo so I couldn't really compare.

My carbs are mounted on a TR4A manifold, that's for sure, and were on my car when I bought it. I had always thought they were original to the car, since it's a 1962 (build date, registered 1964) and almost surely came with H6s originially. I'd never really done anything with the SUs, I knew little about them and set the car up with Webers about a year after I bought it. That was because my parts supplier took that long to track down an intake manifold back in the pre-Internet world. He had to order it from Australia, he said.

So, there is a possibility these SUs are from somewhere else, then, and may or may not be HS6s, or may or many not even be SUs! I'd considered putting them back in usable order once the car is back on the road, to try and see how I like them on a rebuilt engine. Now I'm not sure if I will do that. We'll see.

Thanks for the info!
 
Hello Alan,
certainly the description of the float chamber fuel outlet and the knurled mixture nut are not S.U..
The benefit of a variable choke carburettor (S.U. or Stromberg)is that engine fexibility is improved. Running sidedraught Webers or the like on a road engine may give slightly more top end power but loses out on driveability.
S.U.'s, in particular are easily set up, and maintain their tune for long periods so need very little 'tinkering'. Unfortunately, people tend to do just that with poor results.

Alec
 
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