Welp... got most of the work done on my crusty-ass mower; turns out under all those Ford-Taurus-inspired plastic covers, this is just a old-school valve-in-block 6.5HP Tecumseh. Well hell. Now I know why it's a oil-leaker (admitted by previous owner as the reason he was selling it for $25 Canadian pesos); these old beasts all have a PCV valve that blows out due to phenolic plastic parts breaking down.
Sometimes one gets lucky tho, and it's just a bad gasket under the PCV; hopefully that's the only leak and the lower mainseal isn't gone as well. Oh, and my "fix everything that goes wrong with a weedeater engine" kit just arrived.
mnem
*currently practicing another nearly-dead art: resurrecting the threads on a rusty shoulder-bolt with a needle file*
Tecumseh went bust quite a few years ago. Good luck getting parts for it.
Victa in Oz still used them till a couple of years ago-----I'd much rather have a Briggs & Stratton any day!
That said, I haven't had much luck with small engines.
Car engines, be they fours, sixes, vee eights, whatever, I have very few problems with, but mowers, chainsaws & "whipper snippers"-----------aaaarrrrgggghhhh!