Small Engines (Lawn Mowers, etc.): Briggs valve timing, push rods, valve timing

Question
My neighbor replaced the valves on a Briggs 31P777 type0296-E1 and now the engine won't start. He said he turned the crank about one turn to make it easier to install the head. What is the procedure to get the valves back in time? Thanks John

Answer
Here is a link on servicing the valves:

http://engines.myfaqcenter.com/Answer.aspx?p_faqid=3441&body_0$tbKeyword=valves

Here is a link on timing the vavles:

http://engines.myfaqcenter.com/Answer.aspx?p_faqid=4&body_0$tbKeyword=valves

Why did the valves require replacing?  Are the push rods bent?  What is the valve to tappet clearance?

Let me know.
Eric