I am new to both this forum and zcars. Having recently purchased a 1983 280zx (non-turbo) and proceeding to fix it up I have run into a problem and not sure where to go next. I have adjusted the per the manual and now have this problem. As I increase the RPMs and watch the timing advance suddenly at about 1800 rpm the timing drops back to about 2 degress BTDC. Then it continues to advance as the RPMs increase from there. Does somebody have any idea what might be causing this? Thx, Mike