Adjusting valves, noise from timing chain adj

[blue85']

I am inching towards getting a parts car engine running. No idea how long it has been since the engine was last run, but I would guess 10-15 years.

In the process of adjusting the valves, I was hearing a metallic click about once per revolution. In looking around, I see the timing chain tensioner is moving (taking up slack?) in towards the timing chain about half an inch and then snapping back to rest, causing the noise.

Never seen or heard such before, but all of my previous adventures have been with running diesels.

Any thoughts about what is going on? and how to correct it before firing the engine up? Does a lack of oil pressure have anything to do with this issue?

Thanks,
Jason