it was definately hitting as you can see the marksin the head and the surfaceof the piston is clean in that area. even with head gasket thinknessinto account i prefer not to run positive deck height to allow for stretch at high rpm. these pistons should have been machined. it is easy to miss if you dont how to build and engine but dont really check for tolerences.contradiction in terms i know... but there are plenty of guys outthere that know how to put and engine together in their shed but dont think to check clearences.

as for the pistions. we are not talking about little chips or detonation marks here. a third of the pistion top lip (concidernig it is a dish type de-comp piston) has broken off to the ring lan leaving the in tack all in one go. thatis not detonnation. thats fatigue.