I had that same problem immediately after reassembling the heads on my 3.5 after doing valve jobs and valve stem seals - I had 2 rocker arms come off, one fell completely off and the other got wedged diagonally and put a huge gouge in the cam lobe. I ended up replacing the cam and both rockers for peace of mind but never did figure out why they came off. It ran like crap and made lots of noise just like yours is doing - that would be a far easier and inexpensive fix than replacing the motor.

The diagnosis is that your motor sucked in a butterfly valve, but what got damaged that is causing it to run poorly? Does the shop think that it only bent valves? That's not a terribly difficult fix either - a few valves and guides, plus new gaskets and valve stem seals just because you're there.

Last edited by ryany; 07/09/13 12:05 AM.