Timing

I have a 1989 Mitsubishi Pickup 2.0 engine.I bought this truck brand new in 89.It only has 108,000 miles on engine.I recently found out the cylinder head was cracked,I replaced head,truck runs but will not idle or doesn't seem to have the power it should. I'm not sure but I think it may be in the timing,have set the timing several times but the truck just don't seem to run like it should. Is there a trick to setting the timing and getting it just right??? Any help would be appreciated.....