Needles:

Originally HS carbs had fixed needles and the jet had to be centred on the needle to prevent the one rubbing on the other, causing wear and upsetting the mixture. North America changed to swinging/bias needles on AUD326 carbs/18GH engines in 1969. Home market cars didn't get them until 1971 with AUD492 carbs on 18V engines.

Fixed on the left bias/swinging on the right, with guide and spring (not to scale): (Moss Europe)

Needles have 13 to 16 'stations' or positions from butt to tip, narrowing progressively, so as the throttle opens and the piston rises there is a progressively wider passage between needle and jet hence more fuel is drawn through to maintain the mixture strength. The diameter of each position is what gives a specific needle its two or three character designation.

Jets: As above needles changed from fixed to swinging. The jet bearing kits differ between the two - WZX1341 for fixed needles and WZX1442 for bias/swinging needles, the difference is that the jet bearing for fixed needles has a larger clearance in the jet nut to enable centring, that for bias/swinging needles is basically a snug fit in the nut to hold it in one position, the needle moving to fit the jet.

HS jets - front AUD9141A, rear AUD9142A: (Moss Europe)

The above shows the jet complete with gland nut AUD2129, washer AUD2193, seal AUD2194 and ferrule AUD2195 which are all available separately. The nut goes over the pipe with the ferrule partially inside the pipe and protruding though the washer and seal. As the nut is tightened the washer compresses the seal without tearing it, and the ferrule ensures the seal is kept in position and doesn't block the pipe as well as forming part of the seal.

HIF jets - front (black) WZX1454A rear (white) WZX1455A for the 4-cylinder, left (black) WZX1452A right (white) WZX1453A for the V8: (Brown & Gammons)