Item #12 above is a pretty common myth- - - -since piston rings are in constant motion, rotating around the pistons in a random fashion, it's not uncommon for ring gaps to align- - - -momentarily. I have documented this, using a "training engine" with a quartz window inserted into a couple of cylinder walls to allow observation of the pistons in motion with a strobe light. At one time I had a videotape of the running engine- - - -the rings can be observed moving around the pistons in a very random manner. It's a good idea to stagger the ring gaps on assembly, but expecting them to stay that way is an impossibility.
The only exception is on a 2 stroke engine with ports in the cylinder walls. Those pistons have dowel pins in the ring grooves to prevent the rings from walking- - - -to keep the end of a ring from hanging up in an open port.
Jerry
