HELP CAS WONT TURN!!!

[Alexvi12]

Ok so I've been having issues with my 1990 Nissan 300Zx NA. Whenever I'm riding in my z if I'm low on the throttle it burbles a bit and backfires a little as well. So i checked the timing and it was about 45 degrees off . However i tried losing up the three bolts for the CAS to adjust timing but its stuck. Ive already hit it with PB blaster multiple times and even though i probably shouldn't have tried hitting it with a mallet and screwdriver to see if it would loosen up as a last effort. ITS STILL STUCK. Any recommendations on what i could do.