An appeal for help

[Nick Salmon]

A neat illustration of the old adage that if you think the problem is the carbs, then it's the ignition - and vice versa. Glad you are sorted.

[Alan]

For those struggling, a good option is to have your carb set up properly on a rolling road by someone who knows what they are doing. YeRs ago, SU Carbs used to provide this service - sadly not any more. It might cost a few quid, but could save days of messing about, and remember each new needle you try costs £8+postage.

[Ian Williams]

Early post war carbs also have no spring, Type H will typically be encountered and an awful lot of those have weighted pistons.

[Chris KC]

No.5 Ian? Or No.6?

[Mick Hanna]

I have 2 x 1 1/8" SUs. The one fitted has the aluminium (?) piston; the other, which will need rebuilding one day, has a brass piston. 

I seem to remember reading on the old forum that the aluminium piston uses a spring, and the brass one is weighted and doesn't require a spring. Discuss.

Thanks again everyone.

[Ian Williams]

No 5 seems to work well in my experience Chris, may not be perfect in every car because of the number of variables but a good starting point, I am suggesting this for a 20/60 cam. No 6 is richer so possibly better suited for an engine in full race tune perhaps 30/70 cam, others may have alternative suggestions but I don't think these will be too far off. BTW these are considerably richer than an AN needle, and are for an 1 1/4 SU whereas the AN will be suited to a more std engine with a 1" or perhaps 1 1/8" SU.

[Chris KC]

Good info, thanks Ian