I always leave the pistons alone! I'm aftraid of getting particles on top of the rings. There shouldn't be much on the pistons to worry about anyway. If the valves have a buildup on the manifold side I take em out and scrape them real good.
After rereading your post I see you do NOT have the head off yet.. Not to worry the combustion chamber does not look like the backs of the valves.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

professional bovine relocation specialist