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.
Ha! That's funny that you mention the 8-eyebrow pistons. When I tore apart my 1969 400 engine, I had seen reciepts that it was rebuilt back in 1992 and saw that the guy who did the work replaced two pistons and once I removed the heads, I noticed that he replaced the the two original pistons with two 8-eyebrow pistons. I thought that was odd, while I also had always thought the engine was lacking some power, I always chalked it up to needing a rebuild because the odometer had not worked prior to the engine rebuild so I never knew how many miles was on that last rebuild. I did still have detonation issues and I have #16 heads also.
