Rover Sports Register Forum

Has anyone done this?
i.e. Fit a Pre-war D3 downdraft SU to a Post-war car? In my case a P2 Tourer. I note that the inlet manifolds are the same, so the SU should bolt straight on, BUT what about the throttle linkage? As far as I can see in the parts book the links for both SU and Solex appear the same, but there are cables described (but not shown) as " throttle control complete" and a "mixture control complete" The latter being superseded by the magic starting carburettor controls for the Solex.

It has been done, I have seen twin D3s fitted to an adapted '47 14hp inlet manifold. The 2 cables were for independent choke and a hand throttle , 2 knobs on the right hand side of the dash board. The throttle cable pulls a lever that acts on the throttle linkage and opens the butterfly slightly.

Hope this helps

Mike

Thank you Mike...One SU at a time! my carb's original use was on a Wolseley 12 (1547cc)1937-46) with Standard needle #4, the Rover 12 had a #5. Spring ,float etc all seem to be the same.
I may have a problem fitting the Solex Air cleaner! But I can put a pancake one on in the short term until I can track down a pre war one perhaps. A manifold to look out for would be the Rover 10hp(!) Police spec of 1936... it takes a pair of HV2's apparently.

I’m pretty sure the Burlen site lists cars, SU carb type, needle No and spring etc so should be easy to see which ones were used with the Rover 12. I seem to recall there were several different needles used on the 12, no doubt as the performance increased with the change of cylinder head and inlet manifold. My Tourer is running on two No 4 needles at present but I think No 5s might be more suitable as this was the original set up as far as I can tell. I was thinking this might be more economical and I do get about 24 on a run. However, I do such a limited mileage that it really doesn’t matter! I bought a matched pair of downdraft D3s from a Wolseley when we were at the NEC a few years back. Got them for about £100, thinking I might want to convert my Saloon to twin carbs but I haven’t got round to that. The carbs appear the same as the Rover ones except they are designed for a different air filter. Sounds like yours might be the same.

Tony

Very Interesting! Yr=e I got my information from the SU handbook 18th edition(!) picked up at the last Goodwood Revival! (Burlen by another name!)
there are no twin downdraft SU set ups listed under Rover that I can see...there is an exciting 1939 16hp with triple D2's though!
Wolseley twin D2 set ups are limited to a Derrington 4cylinder Hornet Special in 1931, then a "Scotland Yard" 6 cylinder 14/56 from 1937 then some more 14hp & 16 &18 & with D3's and 21/25's with twin D3's...Big stuff

David,

This discussion got me thinking about carbs, which I haven’t done for a few years. My ‘36/‘37 P1 Tourer is fitted with two H2 downdraft SUs. This was an optional arrangement available pre-War and used on a number of Works rally cars and, I believe, Police cars. However, I have never actually seen another Rover similarly equipped or even a picture of the set up. I’ve never found technical reference to a twin set up for a Rover 12 and it was Burlen who suggested trying No 4 needles when I rebuilt them.

The H2s used are identical to the one fitted in my ‘37 P2, which is the same type used on all the pre-War P1 and P2s I’ve seen at shows. The H type carb was in very common use at this time but more usually as a side draft, which had the damper installed. The HD type was a later (post War?) development, I believe.

The pair I bought as spares were labelled by the seller as HD3s, leading me to assume mine were the same. However, I now realise they were incorrectly labelled and were, in fact H2s. The ‘2’ referring to the butterfly/throttle size of 1 1/4”, i.e 2 x 1/8” over 1”. I’m sure you are aware of the different types and designations but I wanted to clarify for the benefit of anyone else reading this thread to avoid any confusion over what was fitted pre-War.

So, your proposed HD3 would be 1 3/8” in size and very similar to the H2. Being larger diameter it should provide improved performance and better suited to the later, and more powerful, post War 12 engine.

Tony.

My SU has arrived & it IS an HD2 (1.1/2") It will be a bit of a challenge making the links & fittings all work, but it is a brand new unit!

Correction ...1.1/4" of course