I removed the inspection plate from the oil pan on my '21 to look inside. Everything looks great inside. The engine has been rebuilt and has not been started yet. Pistons, camshaft, lifters, and timing gears are all new.
Sometime in the 95 year life of the car the bolts in the plate have been tightened so much that the plate was bent around the bolt holes. As thick as the plate is I can't understand why someone would ever tighten it that tight.
Oh well, such is life. Pound the dimples so that they are flat again and proceed.
Because they're notorious for leaking, so "tighter is better" mentality takes over.
Well they leaked obviously they weren't tight enough! They are out there if it leaks tighten it,if it breaks off it must have been a weak bolt.