View Full Version : TR5/TR250 Carb setup on TR250

07-08-2013, 02:43 PM
Hi Guys

OK, first of many questions for the TR250. Car is currently fitted with dual Strombergs. PO reports that these carbs came from a TR6. From the photos, can you guys tell me if this carb and manifold setup will work on the TR250?
There are no smog requirements for a 1968 car in California, so I don't have to contend with Smog laws. But, I do need to make these carbs work or obtain another set.

It looks like I need a port for crankcase ventilation (rocker cover plumbed to intake manifold?) and a port for the brake servo unit (also plumbed to intake manifold?). The dizzy has vacuum advance diaphragm (actually, two diaphragms) that would need to be plumbed to the carbs (I assume).

So, I'm trying to figure out if this is a workable set of carbs and how to plumb them up? Any suggestions, advice, and photos are appreciated.


https://i987.photobucket.com/albums/ae352/PatGalvin_bucket/TR250/031Large_zpsb27be67d.jpg (https://s987.photobucket.com/user/PatGalvin_bucket/media/TR250/031Large_zpsb27be67d.jpg.html)

https://i987.photobucket.com/albums/ae352/PatGalvin_bucket/TR250/029Large_zps35fcf1dd.jpg (https://s987.photobucket.com/user/PatGalvin_bucket/media/TR250/029Large_zps35fcf1dd.jpg.html)

Geo Hahn
07-08-2013, 03:07 PM
Those appear to be late ZS carbs that have temperature compensators, 'choke' using the little plate with holes and no provision for adjusting mixture (apart from changing needles).

Were it my TR250 I would be tempted to source the correct set of carbs rather than spend time or money making these work. IMO the 250 is a valuable enough TR to be worth setting up right even at additional cost.

07-08-2013, 04:32 PM
Thanks Geo, exactly what I wanted to know.

Can you tell me what the correct set of carbs is for the 250? Or, which model years would work?

Much appreciated.


07-08-2013, 06:00 PM
Those do appear to be somewhat later carbs; but I believe a TR250 is supposed to have "emissions" ZS carbs, with fixed needles and temperature compensators. The later carbs may actually be preferable, since they did incorporate a mixture adjustment (inside the piston).

I'm not absolutely certain, but I think that is the wrong intake manifold for a TR250 as well. Should be (I think) a separate port on top for the PCV valve ?

On a 250, the distributor retard port is supposed to go to a hokey throttle-operated vacuum valve, which supplies manifold vacuum to the retard module only when the throttle is closed. The advance port goes to a special port on the front carb (I think).

The carbs you have would work well enough, I think. Run the servo vacuum line to the big fitting in the intake manifold, then tee together the line from the rocker cover with the two ports sticking out of the carbs at an angle and the line to the carbon canister (two tees). Cap the distributor lines, set initial timing to 10-12 BTDC.


07-08-2013, 06:29 PM
The carbs themselves are made up like the pre 73 carbs...if they were TR6 carbs. Hard to tell without knowing where the vacuum nipples are located.
I don't see one on top of either carb so they may be the 72 version..if they were TR6 carbs
The throttle bypass valve housing could be changed to the type found on 250's and 69's as well as 74's.
Internally, it's hard to tell from a picture if they have adjustable needles or not.
Anyway with all the corrosion, they might present a problem even if cleaned and polished, particularly with the air valve.
However, the TRiumph roadster carbs are all interchangeable as far as performing their primary function of feeding fuel and air to the engine.

07-08-2013, 07:40 PM
Hey guys. For this initial phase of "let's get this thing running reliably", I'd just like to identify a carb setup that would be easy to install and tune. I don't plan to add back all the emissions controls, even though they were stock in 68'. I will keep the car fairly original, but I just can't see adding back charcoal canisters and vacuum tubes, if not required. Are there some other model Strombergs that you'd recommend? I don't mind buying either a rebuilt pair or maybe picking up a used pair (in slightly better condition) and rebuilding myself. Ultimately, after the kids graduate from college, I'm hoping to find a few grand so I can go through the engine - at that time, I'll probably want to set up triple strombergs or some other carb setup.

Thanks for the advice. Let me know what you think about what carbs you'd source, if you were not going to use these ZS carbs. And if manifold is useful or another manifold is needed. I'm not interested in running the triple webers on a stock tuned engine.


07-08-2013, 09:06 PM
The "hot setup" would probably be a pair of SU HS6 carbs. Simple, almost a bolt-on, many tuning options. Only problem is price.

Or better yet, a pair of throttle bodies and an aftermarket ECU. Serious tuning potential there.

But if it were my car, I'd probably just rebuild what you've got and go on until you're ready to rebuild the engine as well.

07-08-2013, 10:33 PM
Those are later carbs, the CD-2 designation was used for many if not all the later Strombergs, but their were various flavors of CD-2 with variations, starting with the TR250, which did have early emission strombergs. You can run the car with any TR6 carbs, but they had variations on the vacuum mechanism, the TR250 and I think early TR6 had vacuum advance and vacuum retard, later cars I think just had a vacuum retard, maybe some also had advance, you want to match the carb and vacuum plumbing to the distributor, which usually isn't to hard to do. (Your car should have the vacuum advance retard distributor, with two vacuum attachments) The tr6 carbs I got with my TR250 (must be a trend) were from circa '73 I believe, and only had a vacuum retard shunt, I drilled a hole for ported vacuum over the center of the throttle plate when closed and, JB welded in a tube and plumbed it to the vacuum advance on the carb. didn't worry about the switch and plumbing to the vacuum retard, which as I understand it does not enhance performance and is purely for emission controls. It ran fine with this setup, but I later switched to TR4A Strombergs and it runs even better and is easier to tune. I picked up the early strombergs on ebay for $50 and rebuilt them myself for about $100 in parts. The TR250 did not have the carbon canisters or air pumps, or fuel tank venting or anything like that, the emission controls were purely in the carb/pcv/vacuum mechanism. Moss paper TR6 catalog has a list of the various carbs used and their numbers, their should be numbers on your carbs you can match it to. Sorry for the run on with no line breaks, but the new forum and my new computer don't seem to want to let me do line breaks.

07-09-2013, 05:46 AM
The poor man's hot set up, TR4A Strombergs, look similar to stock, no emissions BS: https://i207.photobucket.com/albums/bb196/grglmn/newcarbs.jpg (https://s207.photobucket.com/user/grglmn/media/newcarbs.jpg.html)

07-09-2013, 11:09 AM
great photo and setup. Thanks


07-10-2013, 12:02 AM

There's a pair of TR4A Strombergs on eBay now for $150. There's also another listing for what claims to be a TR250/early TR6 intake manifold for $100 although I'm not sure about the PCV port as Randall mentioned and glemon's pictures shows.


07-10-2013, 01:50 AM
I just checked the carbs on the two spare engines I bought recently, one set is C3508, which is for a 73 TR6, the other is C3150, from a very early 6, engine number CC25562HE, believe these are the same as the TR250 carbs, they are set up for the vacuum advance and retard (or as I call it the push me pull you) distributor. https://i207.photobucket.com/albums/bb196/grglmn/EarlyTR6carbs_zps1b623c5c.jpg (https://s207.photobucket.com/user/grglmn/media/EarlyTR6carbs_zps1b623c5c.jpg.html) Sorry for the crummy camera phone pic, but that is I believe the correct set up for a TR250 and early six, so thought it was worth posting