i have a su carb size 1.5 inch would i be best using it or a weber 45 for a slightly tuned 1275 a series? plz get back. cheers

You can run a 1.5 with a red spring BQ needle (according to page 93 of Tuning the A Series Engine by David VIzard).

I run a 1.5 with a blue spring and E3 needle on my 998 with a mod. head and 3 branch.

David

1275 go for an 1 3/4 hif su or a 45 on a proper manifold

Weber is not a lot of gain for the money including jetting etc. S.U. is easier to keep in tune and much more available, also more economical on fuel. If you can get a twin S.U. setup even better

For the 1275 I am building for the 7, I have both a set of 1.25 SUs and a 45 dcoe set up. I want to experiment using the Vizard book set ups to see if I can tell the differences. The Weber should be better at top end and the SUs should pull well but start to loose a little at top end. I have a feeling I will be happiest with the SUs.

D.

Vizard book is well and truly out of date find a late MG Metro in the scrappies and use everything off that -- find one late enough and will even have hardened valve seats for unleaded.

MG manifold can also be modified to make it even more efficient, worked well on my old mini pick up with modded MG engine, pulled like a train and gave good economy if driven sensibly.