I have 72 su's on my 260 and the linkage or the throttle cable (or some other cause that I don't know) seems to be sticking. I am not sure which one, but when ever I am in 1st or 2nd gear the car jumps when I step on the throttle because something is sticking. The only reason I think it might be the linkage on the su is because when the engine is warmed up it is not as sticky. My dad talked to a datsun mechanic and he said that many z's are like this or worse. The way it feels when I drive I know that there has to be some way to fix it. It could be as simple as lubricating the carb linkage or changing the throttle cable, but if you have any ideas or your are experiencing this your self please tell me. Thank you. - Ben

I've had a couple of Zs and this happened on both of them - I never really cured it on the 1st, but with my current one (a 74 260Z) it was simply a weak spring on the front SU. I literally bent the bracket to stretch the spring - and bingo! I can idle at around 650 - 700 RPM (bit lower than recommended I know, but I think it sounds better - makes the engine sound more like its in danger of biting the legs of any pedestrian who crosses at the lights.

Good luck