My 65 d100 sat for 27 years (that I know of) with the timing cover off. It had the loosest timing chain ive ever seen. when I looked down into the pan, I saw something weird sitting on top of the oil pick up. I reached down with one of those spring loaded claw tool things and pulled out a giant lizard. He was fully marinated in 10w40. This made me decide that I would get the mighty poly engine running. Put a chain on it, rebuilt the carb, points, condenser, and a new fuel pump/filter. runs like a champ now and recently cold started at 17 degrees during our current storm. Oh yeah, I did pull the engine to fix numerous gasket leaks. Inside the oil pan where the lizard was living I also recovered, a mouse, a rat, three baby frogs and dozens of bugs.