while ive never had an issue with standard heads, my only slant head leaks like a sieve and just warps by design. theres no solid beam under where the plug is located. right where it leaks. they all look the same from what ive seen. bin model in my opinion.
other people dont seem to have this issue apparently. so. ignore that.
flat surface, as flat and solid as possible,glue on 100-240grit sandpaper, gently rub sealing faces until completely contacting, both cylinder and head. sorta rotate the thing around on the sand paper, dont sand in just one direction.
always torque down in a cross pattern, after first nipping em tight by hand, carefully wriggling it all to make sure they all pull equally at first. half turn at a time, round and round...
you tighten just one first, whole head will tilt and warp, never sealing.
never had issues with stock studs, nuts or...no. the washers are POS. gaskets are...ok
a very slight smudge of oil is sorta normal on anything with a head gasket. a nasty poppin squeakin noise that tends to clear up as the engine gets warm...thats a leaking head gasket! occasionally you can feel the blast