ok so i bought this wrx and it had bent valves, it looked as if someone tried to redo the timing belt and didnt time it right and cranked it and bent the valves. the valves were slightly bent but enough to not build compression. so i got the heads rebuilt and reassembled. when we started it it ran fine then EEEAAAAAAKK and the motor moved as if it had load on it(rpms drop slightly). then idles good, then again few seconds later EEEEAAAKK. the mechanic thinks its a rod bearing, or bent rod. but idk it didnt sound like a knock at all... could it be my rollers(bearings) on my timing belt system freezing...and maybe the reason the for jumping time in first place? what do you think? i dont want to tear it apart again.

so today im gonna see if its..
-throw out bearing
-something on the accesory belt system freezing