So what i am dealing with is a 74 260z coupe with a 5 speed from a 280z and the starter on it is from a 280zx.

Initially I use to have issues with the key ignition just clicking over, so I bypassed that with a push start to turn the starter over, after that resulted in the same outcome after a good while I decided to install a stand alone starter silinoid and ran the push start to it then to the starter.

Now my issue is the start just spins, Ive had the started tested at a local autoparts retailer and it passed, I even tried a new starter and new battery all with the same outcome, When looking at the flywheel it doesnt seem to be to far gone that it wouldnt be engaging.

One odd thing is if I jump the starter it will spin but shortly after that i can hit the push start and it will engage... SOMETIMES.

I am really baffled with what to do from this point if anyone has any ideas I would greatly appreciate your help.

Did it ever work right, before the bypassing? Maybe get a new ignition switch, both of my cars have newer ones. But it does sound like your starter teeth and flywheel teeth aren't mating just right. I just compared ZX starters to Z's and their part numbers are different and a lot more $$.

Did you put the five speed in or did you buy it that way? If it was previously an automatic, it might still have the spacer behind the flywheel. That would hold the flywheel away from the starter.

Assuming it is not the auto-trans swap issue Zed has suggested, it sounds like the overrun clutch in the starter is bad. How does the auto part store test the overrun clutch? I suggest they can't.

It was working properly before the bypass until all it would do was click over I bypassed the key ignition. As for the different starters I had purchases a new 260 starter and it did the same thing. ( the only difference between the starters should be the amount of tork they put out )When I bought the 260z it had the original 4 spd in it and i swapped it out for the 5spd, Never was auto. And the overrun clutch? I am sorry I guess my knowledge of starters isnt that advanced, however I would assume the new starter would have had an overrun clutch that wasnt bad.

If anyone needs pictures of what I am dealing with just let me know and ill go get what you need to better assess the situation.

Take a good look at the ring gear on the flywheel. It might be worn or have moved. A small mirror through the starter hole might be needed to get a good look.

Typically if the ring gear is going bad, you'll hear a terrible noise. The fact that it occasionally works when you jump it tells me that there is an electrical problem in the car not the starter. Lack of full power to the solenoid on the starter could do it. I'd clean all elec. connections including grounds on that circuit and check for full voltage to the starter solenoid. Mark in Portland