[Jac Mac]

Have a real close look at the ends of the top rings to make sure that they have not been fitted with too tight a ring gap to the cylinders. If you get into a marginal detonation or even preignition at low engine rpm the sudden temp spike can cause a rapid cyl temp rise that will cause the top ring to expand rapidly and butt the ring ends. The ring then has no where to go and the drag of the ring in a bore which is now 'too small' will pull the top ring land. This is even more prevalent in 'stroker' motors with short pin height piston's ,Top ring gaps in these combos should be increased to around 0.025" or 0.028" , maybe even more if you know that it will be subject to this sort of thing. Second ring gap has to be increased slightly as well.

While some may be keen to blame an engine builder for this, it quite often happens due to a combo of things- stale fuel-cold motor/hard acceleration- too 'fast' an advance curve- 'lugging' the engine in high gears @ low rpm. etc etc.

Jac Mac.