Technical Carb change

[whsdavies]

I have fitted a 650 engine into my 500.
As I am familiar with S.U. Carbs I would like to fit one. I see that some suppliers are listing a manifold to suit.
Has anyone experience of this mod?

 

[Toshi 975]

I have seen a couple of SU carbs fitted to engines in 500s and am told they work well. I think that it is the 1 1/4" HS2 Morris Minor type that has the same flange as the rarer Dellorto so they fit that manifold. If you look on the Club126uk forum there is a guy there who has just fitted a SU about a week or so ago. Very versatile carb as I converted one to a downdraft and fitted it to a 1947 Sunbeam Talbot and it was way better than the original Stromburg.

 

[stevehg]

Hobbler should be along at some point, and he has direct experience of SU carbs on 500 engines.

cheers, Steve

 

[the hobbler]

Did I hear my name being called---thought my ears were burning! Although I have not fitted an SU (yet) I have looked quite deeply into the possibility. The FZD was often used as a direct replacement on Mini-coopers etal as the fitment angle and the flange measurements are identical to the HS2--a 1-1/4inch semi-downdraught carb. So, as Toshi mentioned, you use a FZD inlet manifold. I have discussed jet/needle combinations with 'Burlen Fuels' (who now own the SU name and brand and make the carbs) as well as having a sneaky look at the owners hand-book for the 650cc Triumph Thunderbird motor-bike. The Police versions used the H2 carb (1-1/4 side-draught), and the engines produced 34bhp at 6,400rpm. The consensus was to use the following as a starting point:- Right-hand carb )puts the float chamber at the front of the engine) with the remote float-chamber (the angle of the float chamber on this variant is set by using special washers between the float-chamber and the carb body), 90thou main jet (part no. AUD9142), H7 needle (part no. AUD1271--this needle was used when the bikes had a 'chair' attached), or H9 needle (part no. AUD1273--was used on 'solo' bikes) and either an red spring (part no.AUC4387) or a blue spring (part no. AUC4587). The throttle linkage shouldn't be to difficult to arrange, but the choke will either need a much longer cable (it comes in at 90deg to the Weber arrangement) or a secondary pivot arrangement where the throttle linkage pivots.
Ricambio International listed a 'SU Carb', but they did not know which specific carb or what needles/jet to use. The SU carb is a very good, simple carb that has given fantastic service over many years to thousands of car/engine permutations--I can see no reason why it won't work on the 500. I would however, if possible, recommend that you get it set up on a rolling road--so much easier and much more accurate.
Where do you live?
I hope this helps you sort things out

 

[Toshi 975]

I still have a complete SU HS2 carb left over from my long gone Morris Minor days if anyone else is interested in this conversion. Message me if you would like it at a bargain price.