Mk2S Twin HS4 - needle question

[Tex1965]

Please excuse me - I am sure needles have been discussed million times, and there are tools and charts available how to select correct needles. Used to fettle with such when I raced my Volvo 122s (historic FIA appendix K) .

A Mk2S has stood unused for almost 20years. Before it was forgotten, a new set of HS4's were installed together with aftermarket inlet and 280..286 cam. Have not fired the engine yet, needs to clean fuel tanks and carburettors first. Few other issues too.

The needles are (spring) AAU , 1293cc, 10,3:1 comp, Maniflow LCB + exhaust, 280..286 cam.

As the setup is nowhere near original, so I just don't have the starting point for a needle search. What needles you would recommend? Of course, when engine is alive and kicking I can do my "testing", but here's no rolling road capable for tuning so I am on my own with it.

Greetings from northern Finland,

Rauno

[winabbey]

The twin HS4's fitted to the Police specification Cooper S in the late 60's and early 70's here in Oz used blue springs with BG needles.

[Desmodromic]

My recent experience has been with with twin H4s and fixed needles, but for your HS4s with bias (spring) needles, I think you might as well continue with your existing AAU profile ones. No need to buy more needles on spec till you know she'll start and run.

The table here: https://www.minimania.com/SU_Carbs___Qu ... ection_733 suggests a couple of alternative spring needle profiles.

To compare them to your AAUs I'd suggest: http://www.mintylamb.co.uk/suneedle/. I've just done a quick comparison, and all the needles suggested by Minimania are slightly richer than the AAU, but only at higher revs. They do specify using K&N or no air filter, so you would expect the needles to be richer. I think AAUs should at least get you going.

Good luck.

[Allen Brzeczek]

Have similar spec engine with 1-1/2" SU's fitted with long open bell mouths, AAM's and red piston springs work for me, but i agree that you should perhaps test run with what you have and refer to table and compare profile before making any choice as I did, might have been lucky but in my case the transformation was remarkable, smile every time I go out - cannot find or recall the needles I replaced but set-up had previously been used on another Mk 1 Cooper S.

[Tex1965]

Thank you, very helpful. I shall do just that, start with AAU and go from there.

SU's now cleaned. While waiting for new needle valves & jet assemblies to arrive, I managed to blew up clutch hose when trying to get clutch working.
Slave cylinder is stuck (hopefully it is slave cylinder, not the clutch).