Thread: Solex CD175 on Series 2A 2.25

I just fitted a Solex CD175 dashpot carburetor from a ’82 Range Rover on to my ’61 Series 2A.

I’m still fine tuning it but it’s already an improvement over the Zenith 361V and since I couldn’t find much on line about doing this I thought what I have done may be of interest to others.

Some background, so far I have tried the original Solex downdraft that was on the vehicle when I got it, a second less worn solex with a new kit in it, a weber carburetor and two Zenith 361V’s. While the old downdraft carbies all mostly worked OK, they all had various issues…361V’s can be hard to get the idling right when hot and cold (I do know about the “warping” issue and how to fix it) and the accelerator pump on the Zenith has a non-adjustable valve that makes it difficult to get a correct fuel quantity on sudden WOT…the Weber and Solex had other issues…enough about the DD carbies that all petrol series owners have their own experiences of.

I went to an exhaust system place and for $35 had an adaptor made up as you can see in the photo below. It’s not particularly pretty but it works just fine. I do plan to make a shorter neater adaptor but at the time the exhaust guy couldn’t make the 30 degree bend shorter.

I used the passenger side carburetor off the RR because it had the choke (enrichner) plus also the distributor vacuum advance port…the drivers side one didn’t have either of these.

The original oil bath air filter intake fitted perfectly over the RR carb inlet adaptor. I wanted to retain the oil bath filter because it is easy to maintain and was designed to supply the airflow required for this engine. I tried but couldn’t detect any improvement with the air cleaner hose off.

I used the original series accelerator linkage plus the linkage adapter below that I made from some old LR bits that I had. I plan to fit a cable in the future, probably adapting the cable of the 85 RR that I have a spare one of.

I had the exhaust shop fit a flange to accommodate an oxygen sensor in the exhaust pipe and used this with a Lambda meter Oxygen Sensor Information to adjust the mixture via the adjuster in the dashpot and to check the mixture at various speeds.
I got the Oxygen sensor from a local wreckers for $5. I used a 4 wire narrow band type. There are 1, 2, 3 and 4 wire and wide and narrow band types. There are also many different gauges and LED display types to connect the sensor to.

This carburetor has a 0.1” metering jet (I think biased adjustable is the description) and a BIFH metering needle. It works great but I believe is lean around stations 3 and 4 so I plan to experiment with other jet needles…I’m still researching this.

There is lots of information on line about CD carburetors and I guess part of the fun is doing the research. It seems that Solex and Zenith and Stromberg CD175 caburetors are pretty much the same (kits and gaskets appear somewhat interchangeable) however, with some differences depending on what vehicle they were on.
One such useful site is TR250/TR6 Carbs Part I

So what is good about the CD 175 carburetor?
It starts well. Idles smoothly. Smooth acceleration from still to top speed. Deceleration is also smooth compared with Downdraft carbies that “snap” shut. It definitely cruises better at 80-100kms. I haven’t tested yet but suspect better fuel economy. Best of all the research and experimenting is great fun! I hope this may be useful to someone else.

I couldn't figure out how to embed pics so hopefully they are attached.

Hi,
Read your article with great interest and congratulation for having a go.
Ive started work on a 1971 LWB 2A 2.25l. Have been researching what improvements can be make to the engine to improve its overall character and performance.
So I would like to ask you "hows your carby set up is working" as I have a manifold off my 83 RR with two stromberg laying around and if its working well for you I would be willing to have a go at it myself.
Thanks.
Iain.