Thanks Dave.

So the pushrod/rocker interface wears and the lifter doesn't take up slack?

I have also read a lot of comments(not on moparts) where owners are going to a 5w30 weight oil and the tick stops and they drive many thousands of more miles without a failure. Do you know what's up with that?

Or, the tick is just 'there' and they continue to drive thousands and tens of thousands more miles without a failure, and its not the exhaust leak tick.

Maybe they're just living on borrowed time?