Alan is right again, much too much money asked for this job.
Your engine has roller followers and some times, if a valve sticks or hangs open, the follower will be 'kicked' out of place.
This however will not cause an engine knock which was what we were chasing after.
That's one large problem with any forum, the fact that what is described as a knock by one guy is a ticking or clicking noise to another.
We often are led astray by the improper description of a problem.
If the follower was knocked out of place, the engine should have had a definite miss and loss of power.