100% urge you to replace that timing gear. Doesn't sound good at all.

As for the pistons - they are typically fairly stiff when new rings are sliding up and down the cylinder walls. You could have an issue where the rings are too tight - you can check by removing a ring, then sliding it into the cylinder without a piston, making sure it is aligned in the bore (not canted sideways) and looking at the gap between the ends. I don't know what a good gap is, but I do know if it is too small bad thigs will happen. The rings lengthen slightly when warmed up, without enough clearance this will push the ends together and really increase the pressure of the ring on the bore far past what it should be.
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I'm JohnMc, and I approved this message.