what is tighting procedure for head bolts and the proper required torque?

Yes there is. Did you have a machine shop check the head out?

Not sure how far back there information goes but Hyundai as a car manufacturer put a lot of free technical information and workshop manuals on line for Hyundai owners. Check out www.hmaservice.com lots of great information. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online