slipped balancer ?

i have a 350 chevy with the comp 268xe cam in it.inital set at 18,total 36. ran good like this for a year or more.(down most of this time due to painting}. i started driving it and made a few hard passes with it,ran great. heres the problem. it was hard to turn over when warm so i reset the timing to 10 initial. now has severe loss of power and pops and misses. changed it to 12,still no different.went back to 18(according to timing lite). why would it run so bad at 10 .this is not that big of a cam. could the balancer have slipped ?maybe the 18 isnt 18 at all,the dial back says its correct. somethings wrong.anyone got any ideas? thanks

Set #1 piston at TDC and see where the timing mark is... Slipping balancer rings isn't all that unusual with a sbc.

thanks/ i didnt even think about that.