Check the clearance between that crankshaft counterweight and the camshaft lobe it aligns with. That ground area might have been put there to assure there's no contact between the cam and the crankshaft as the counterweight rotates close to the cam. Some crank and cam combinations get VERY close together at certain points. If that's a splash-oiler 235 with the longer stroke, things can get very close!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!