The best advise is to take it back and give installer the option to fix/check or find problem. That being said and if not an option here is a way to prove proper valve timing and not very difficult as these things go. This will also check the balancer if it has slipped on the rubber between hub and outer ring.
Remove valve cover and install a magnetic base dail indicator on the intake or Ex. valve . Set up should be a version of say Comp cams instructions to degree your cam but at the valve its self not at lifter ( generic description and same if overhead cam on or driving valve opening). Any of the big grinders have instructions to degree their cam available on line. Any point or even reading the spring retainer will work as long as a reading can be repeatable. You will need to know cam specs but even specs on a simular cam will be close enough to tell if off as much as 1 or more teeth on cam drive. Now rotate and look very carefully at the @ 0.50 readings compared to the timing tab and balancer markings. If off a tooth it will show crank timing is 30 or more degrees out of wack.
Good luck as it could be a lot of things besides the cam timing but ya have to start some place. Jeff C
