I recently replaced the rear wheel cylinders in my 1972 Z. I have been fruitlessly trying to adjust the shoes. The center part of the adjuster (with the slot the shoe fits into) does not thread in or out when the knurled outer part of the adjuster is turned. Both of the adjusters that came with the OEM wheel cylinders seem to have the the center fused to the outer. Did I get the the wrong part or am I missing something? Thanks for any advise.

Do you have two sets of adjusters or are you describing one set? If the parts are fused you wouldn't be able to turn the wheel because of the slot on the brake shoe. If you can turn the wheel but nothing happens it would be because the threads are not engaged, either because they're fully extended or they have stripped internally.

A picture might help.

The adjuster turns until in full contact with the shoe. I will try for closeup pics,

So it does adjust, but runs out of extension? Did you replace the shoes also? Maybe you got the wrong ones. I think that the later Z's, with the two piston cylinder (1978 and on), use different shoes than the early Z's.

With the kind assistance of Mike McGinnis @ Banzai Motorworks in MD, I seem to have a solution. I was working with the left rear brake. Mike points out that the left adjuster inner part has a left hand thread. With a little force in the right direction, the inner part broke loose. Both of my adjusters have anti-seize on the inner threaded part, keeping them from threading in and out without force . That obscured the solution.