When taking apart your engine, always change your head bolts. Head bolts stretch during the torquing process to produce the right clamp load. Once you disassemble the engine, your head bolts should be replaced to assure you will have the right clamp load during your next torquing process. Before you install your new head bolts, always clean the threads inside the blocks from all debris which could hinder the torque value. Use a molybdenum disulfide paste for lubricant, and head bolt washers for high performance applications.