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Triumph TR6 - Carb Conversion

The carbs on my '76 TR6 are in need of a rebuild. My mechanic has recommended converting the original ZS 175 CD units to Weber downdraft carbs. They read good in the ads, but was wondering if anyone has had any experience with the conversion that they could share. Thanks.


I saw a lot of conflictual advice on weber conv.. You may need a good mechanic or tune shop to solve inherent jetting problems of these carbs. The easiest avenue is to overhaul originals strombergs...
Cheers, JGC
Jean G. Catford

In looking at the manifold set up for the twin Weber 32/36 DGV conversion, you will find a somewhat convoluted path with what amounts to a sink trap routing. It just doesn't look right to me and I have always been a bit skeptical about it. I knew one person that had done that conversion when I was living in Texas and he wound up taking them off and going back to the Strombergs. I would suggest the following in order of increasing cost/complexity:

1) Not interested in "hot rodding" it? Then find someone who knows how to properly rebuild the Strombergs, or buy a rebuilt set Apple Hydraulics, Roadster Factory, etc.

2) Convert to HS6 SU carbs. They are also a 1.75" carb, Moss has kits as well as Burlen Fuel Systems out of the UK. From a performance standpoint, not really that much different that the Strombergs, but the carbs are simpler, so there is less to have to fiddle with here.

3) Convert to one of the triple 1.75" set ups. You can use either Strombergs or SUs for this. I have seen a couple of these (both with SUs) and talked with the owners. They seemed to like the setup, but they had also performed other modifications to the cars. Good streetable set up.

4) Convert to triple Weber 40 DCOE set up. Works best on modified engines, cam changed, port work, bumped up compression, good free flow exhaust. Even better with MSD/Pertronix ignition combination and a light flywheel. Can be a bear to get set up right, but when it is hold onto your hat.

5) Convert over to the Lucas PI unit. All the pieces can be had from from the UK. WIth a mix of new and used equipment, you go go fuel injected for a fairly reasonable price. Since you have a 1976, all of the cylinder head port spacing will line up just fine. On the early engines a change of cylinder head would be required. This can probably be done for about the same or maybe even a little less than the triple DCOE set up. Best of all, the system was designed for this engine. Your camshaft is the same as the later UK cars, the main difference is lower compression and the bolt on emission equipment.

6) Bite the bullet. There's no hiding real money, so go the electronically controlled fuel injection route. Get three of the modified DCOE throttle bodies and a manifold from TWM, the injectors and other fuel system bits, O2 sensor and a Haltech controller. Assemble all the bits, break out your lap top and program your system. Unless the prices have dropped like a stone, this will run about 2 1/2 to 3 times the cost of the triple DCOE set up (why I went the triple DCOE route).

If you decide to go the triple Weber 40 DCOE route I have a set of 3 (never used but was installed on a Datsun 240z). I would consider parting with because I don't want to go through the cost of changing my exhaust manifold to headers and want to keep my car stock.

The carbs are complete with K/N filters but no manifold...the manifold is a Cannon for the 240z

Carb problems? I converted to the down draft Webers and my troubles disappeared. No more flooding, hesitation, cussing. I can't tell any difference in performance and there isn't much improvement in mileage. Converting to triples or fuel injection may be fine for those that want a little more performance, I just don't think that it's worth the money. If you're looking for a good reliable alternative to those pesky 175's, get a set of the down draft Webbers.

Joe Justice

I did the conversion two years ago because I wanted to increase the performance of the car and was getting tired of the tweaking of the 175. Although I rebuilt the original carbs, which is fairly easy if they are in good condition, I have always had minor problems when the car is hot is slow moving traffic. The installation of the webers is pretty straight forward. However, the diagram you get most likely will not match the triumph (my diagram was for a AH). Two things though, you will have to bang in the wheel well a little bit to fit the forward carb and, you will have to tinker with the linkage to get the second throttle to open up. Overall, I am happy, once I got the mixture set, I have not touched them. But, I have not noticed any increase in powere just rather a smoother running engine. Feel free to e-mail me with any questions
Mike P.

This thread was discussed between 02/10/2001 and 04/10/2001

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