Jerry,

A worn camshaft will cause idle problems once it gets pronounced. I've got a 4.5 M117 with the typical worn right side cam. On mine, one lobe has worn through the hardening. What you see is a distinct ridge on the trailing edge of the lobe where the softer metal is exposed.

The hardened surface is thicker than you'd think. You can have some pretty deep grooves without punching through.

Once the cam is worn, you won't be able to set the valve clearance properly (N/A on a 560) so you will hear ticking. It really should affect idle at that point. Mine runs fantastic at higher RPM, but not so hot at idle. I'm going to replace mine in a couple of months.

You should probably turn the engine over by hand and carefully examine all lobes. You can take the valve covers off, unhook and ground the coil wire so it won't start, and crank it over a little at a time. I've done this, but you can cause oil to splash. A helper is beneficial for this. Just crank it over in short bursts. And make sure nothing is caught on the exposed cam when you crank it.

Sholin

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What else, '73 MB 280 SEL (Lt Blue)
Daily driver: '84 190D 2.2 5 spd.