Vacuum on 1968 GTS 340 4 spd.

I did use a piston stop already and found Balancer was off 5' degrees. I remarked my damper . I thought originally my timing was set at 8' BTD but was actually at 12' I now had bumped to 16' to see if it helped but didn't so I'm going to pull it back a bit .I did not no how to check the cam but know will check that with your suggestion. Thanks !