Recently there have been a couple of listings on fleabay of SU HV4 carburettors, in both cases pairs by different sellers.

In both cases they are described as down draft.

I have always thought of SU carburettors as side draft, am I wrong or are there two types of HV4, down and side draft?

Could it be that the impression of down draft is thought due to the inclined angle of the carburettors on the Daimler engine.

You are correct, they are side draught carbs.

Thanks both, thought I had missed something.

My 15 has had a Solex down draft fitted at some time which I have had trouble setting up. I have bought a replacement HV4 side draft which I have refurbished and was wondering before I fit it and tweak the controls if I had the right carb.

Hence the question. Syd

Gentlemen,

My understanding is that the "H" in our ordinary S.U. carb models (H2, HS4, etc.) stands for "horizontal", i.e. sidedraft.
Oddly, I have seen setups referred to as "semi-downdraft" where H-series carbs were used, tilted at a slight angle from horizontal!

I've heard of "vertical" or downdraft S.U.s, and thought they were designated "V". Possibly used in non-standard applications such as military vehicles. I don't know what to make of "HV" carbs. Hope someone follow up with more info, Id love to learn more.

Bob Frisby
Boise, Idaho USA
DB18 & DF302 Empresses

S.U. certainly produced downdraft as well as sidedraft carburettors......
In this case the piston return was with spring assistance only since gravity was not going to help.

This catalogue gives an idea of the wide range of S.U. carburettors produced.

Nice picture "Mr O'Plinth" something I have never seen before, you learn something every day.

Bullens http://burlen.co.uk/?___store=default are of course the font of all knowledge on SU and many other Carbs, there is a load of interesting reading on their site, too much to report here, but a quick read did not show anything about H for Horizontal and V for vertical, certainly the HV4 I have is a side draft so perhaps that is a red herring? Nice try though.

When I was doing research for the right Carb for my 15, I did not find it easy to identify the correct item, but Dave Bennett (Capt Bobo) kindly chipped in and between us we sorted what appears to be the correct type, but we shall see when it is fitted.

Sadly HV4's were used on Bentley and Alvis cars in pairs and in singles on some 15's so they rarely come up in singles.