Yes they do have an ACR (Automatic compression release) takes about 300 rpm to get a good reading .
Also did you check the timing ? on the left side of the engine shroud, should be a round hole kinda low right behind point cover.
When hot timing may have changed enough to make it Knock.
There is a mark on the flywheel you can mark with paint, and use timing light .
You change the timing by opening or closing the points