Most instructions recommend oil after cleaning threads[with a chaser or tap],using new head bolts,etc. I've used anti-seize on head bolts with good results. I usually clean the threads in the block with a brass brush and WD-40,then like a gun barrel,with oiled swabs. right before install.I spray carb cleaner and air to get any oil and gunk out. I always retorque after a few hundred miles and check valves.