SU needle calibration diameters are designated at 1/8-inch increments starting at the top mounting shoulder. Those positions are call "stations". The MGA pushord engine originally has H4 carburetors (1-1/2" throat) with .090" needles and 13 designated stations. The standard needle profiles are shown here. Other SU carburetors may have needles up to 2-inches long with 16 stations. The needle number will be found on the upper shank of the needle. Install the needle with the shoulder flush with bottom of the air float piston (and try to avoid positioning the set screw on the numbers).

MGA 1500   Lean Std Rich Sta. 4 GS CC 1 .0890 .0890 .0890 2 .0850 .0850 .0850 3 .0814 .0815 .0810 4 .0785 .0785 .0780 5 .0761 .0755 .0750 6 .0737 .0725 .0725 7 .0714 .0700 .0698 8 .0692 .0675 .0670 9 .0668 .0650 .0640 10 .0645 .0625 .0610 11 .0620 .0600 .0590 12 .0610 .0575 .0550 13 .0600 .0550 .0520

MGA 1600 & 1622 Lean Std Rich   AO 6 RO Sta. .0890 .0890 .0890 1 .0850 .0850 .0850 2 .0820 .0814 .0810 3 .0793 .0785 .0770 4 .0766 .0755 .0740 5 .0737 .0725 .0710 6 .0705 .0696 .0685 7 .0673 .0666 .0660 8 .0640 .0636 .0633 9 .0608 .0606 .0605 10 .0576 .0577 .0580 11 .0544 .0550 .0558 12 .0510 .0520 .0530 13

Click for a page that will display the needle profiles for comparison.

Click for a spread sheet with more needle numbers tabulated.