sudden timing advance

Thanks for all replies!

The distributor seems fine, and it was not loose.

The springs seem to be returning as they should.

I did a compression test and saw 160-170 psi on all cylinders. This excludes a bad timing chain, or not?

How much slop (in degrees) is acceptable for the timing chain? It would be great if there existed some little window to inspect it, like timing belts have...

As the heads in my engine were really shoved and the pistons are cheap, with no valve relief, I am afraid my little 318 might have some interference now. That is why I am really afraid of breaking a chain...

Thanks again!