Yeah, and if they used those dreaded 8-eyebrow cast pistons, that would also lower compression slightly. There are small scopes that can be used to go thru a spark plug hole, and look around inside, at the piston and valves. I've seen 'em used when teching dirt track engines, to check for oversize valves and illegal pistons. You might be able to borrow one of these from a professional mechanic, if you know one. Or there may be places that rent 'em. Or hey, maybe Auto Zone loans 'em.
There are all kinds, including some that work with your smart phone. But you'll need one that can look both at the piston and at the valves. Some are not that flexible, and do not have that capability.
