SU needle question... TR3

[karls59tr]

If I'm running a TR3 engine with a header and a mild street cam would it benefit me to run the "rich" needle rather than the standard one in the SU's?

 

[dougie]

You need to first determine what your current needles are doing. If they're delivering a mixture that is too lean then a richer needle might be in order.
A chassis dyno will tell you the answer, but you can also check the spark plugs, color of the residue in the tale pipes, use a "colortune" or other device to check for the correct air/fuel mixture.