Kohler Command Pro 15

My Wheel Horse/Toro was running great. I shut the tractor off for a few minutes then restarted it at which time it was hard to start and sounded like an old washing machine. The engine finally ran OK, but made a noise like something was rattling on or near the engine. Using my screw driver stethoscope I traced the noise to the valve cover. The engine has 511 hours on it, the oil level is correct and the oil is clean.

I,m guessing the cam is shot or could the timing chain be part of the issue?

Thank you.

Collapsed hydraulic oil lifter. they can make a strange noise on shutdown, and can rattle sometimes on startup, but seems strange that it didn't quiet down quickly.

Turns out the noise was due to a defective oil pressure by-pass valve. The shop is replacing the valve and the cam shaft.