When my corroded, stock '73 240z cylinder head needed to be replaced, the mechanics installed a new-looking Y-70 head assembly. I think someone else had ordered it for an engine mod and changed their mind. From what I've read it's from a 1980 - early 81  Skyline with L20AET engine, and various other Nissan models. I like it, especially with the AT, not much top end but great mid-range torque. I read Ozconnection's  threads about it here and on HybridZ, searched and searched but never found a manual or other specs (that I can trust).

So how do I adjust the valves ?  No experience so rather not just wing it. Hear some ticking when it's cold but maybe that's normal.

 

Do a detailed Measurement now, then adjust to what a 73 is. That way you can always go back. 

Though I doubt when the techs put it on they knew it was a Y-70 head and simply used 73 specs anyway. 

After reading this link below I think I'm going to put this off. Planning an engine rebuild and valve job as soon as I find the right shop to do it, so they can do it then. Not supposed to be doing anything other than minor maintenance here and don't have another place to work on it. Looks like and all-day job, at least the first time. Did a hot adjustment on my old dodge van with the engine running, also on my chevy, but that's a different can of worms. Should learn to do it though, since it's basic. I watched the mechanic adjust the valves after they installed the Y-70 (from a respectful distance), took about ten minutes. But I go slow and careful when I don't know what I'm doing.

Looked up 280z spec, same as 240z. Looked up 1982 280ZX, it said 0.007 and 0.009 cold,  0.010 and 0.012 hot, FWIW.

If anybody ever reads this and can post a link for specs or a manual for L20aET or Y-70, I'd appreciate it. Maybe I need to relieve the valves a little or something to reduce compression, to run more timing with Calif. pump gas.