Needle for SU carb

[boughtaspit]

Hi all

 

I've just bought a 1975 Spitfire 1500. The engine is standard other than running an unleaded head and a 4-2-1 stainless exhaust system with twin tailpipes. The twin SUs (with standard filtration) are currently fitted with AAR needles but the car is running very rich. Would fitting standard ABT needles be likely to solve this problem or will they be too lean with the exhaust that is fitted?

 

Many thanks.

[Pete Lewis]

just fitting a 421 without any other head or breathing mods i would stick with the std needle and std spring

if its fitted with a yelllow (bed spring) and a rich needle with std filtration I feel you would be too rich over the whole range 

 

do this in stages   try std spring AAR  then  std spring ABT      compare effects

 

Pete

[boughtaspit]

Thank you