Wendell,

 

This piece cant fall if installed right. I'm assuming you built the motor yourself in this same location? Is there any chance it could be an old piece from the original apex seals? These little buggers do sometimes "jump" out of their position while installing if you dont have an ample supply of Vaseline on them.  I guess it could if you had a bridge port cut incorrectly. And if that's the case you could possible see the corner pieces with a mirror. Not a surprise I want to find in my floor for sure!

 

Bob Mears

Supermarine Spitfire