what happened when i replaced my cam was that the current ball stud / height checking tool showed that i did not need to adjust any of them. i did buy the factory tool to check and each one was dead nuts in the middle of the red line. coincidence? don't know the only thing i do know is that i replaced the one bad ball stud, all new rockers and the cam and i made no shim adjustments.
as for your situation that is a big fat maybe. you'd have to look and see (using a height checker) where the red line is in comparison to the ball stud. but believe that there is no mistake where that red line is on the height checker. they know exactly the dimension on the rocker, cam lobe ball stud and valve spring height/shim. that height checker
i made a post last week but it never showed up. in it i had made a comment about putting a new bearing in an old race that had been scored. well that is my take on putting different used rockers on a known good cam. you just shouldn't do it.
the cam rocker relation is unique to each lobe. you would never take out rockers and throw them in a box mixed up then re install on your cam on just any lobe nor would you use old rockers on a "new" cam. note: a new cam requires an initial break in. when you install a new cam you must run up the rpm and let is set for 20 plus minutes so the cam and rockers can break in.
so was your mechanic correct in doing so... don't know i just know that i would never do what he did. now i'm sure he's had a wide spread of customers some say fix it as cheap as you can and some that are the make it perfect customer. he may have miss read what you told him.
i don't recall now. did he replace any ball studs in this process?? if he didn't you may still have the same problem now as you did in the beginning. the tapping noise will come from a ball stud collasping or the rocker/cam is ground down changing the rocker's angle thus releasing the valve spring's force on the rocker and viola a tapping sound.
you may get varing opinions on my take of the rocker and lobe relation and folks who have never bothered with how the rocker and lobe work together. this has just been "IMHO".
1972 350sl Red/Blk 117k
1988 420sel charcoal/Blk 140k
1987 420sel gold/tan 128k
See My Cars at:http://mysite.verizon.net/res0aytj/index.html
Pound it to fit then Paint it to match!
There is only First Place and Varying degrees of last!
Old age and deceit will overcome Youth and Enthusiasm every time!
Putting the square peg in the round hole is not hard... IF you do it fast enough!
Old enough to know better but stupid enough to do it anyway!