He told you to advance the cam from center to help lower ther RPM band. It sucks when you trust someone and they tell you wrong. Wether it was by mistake or otherwise. All you can do is check to see if the valves are bent. If they are you can get new ones and reinstall. If you are lucky and they didn't bend the heads, you will need to look for bet pushrods as well. You'll need to clay the piston for clearance(find out how in the search feature) and aim for .100 exhaust and .080 intake.