Wow. Kurt, is the stuff kinda sticky, or is it like fuel varnish - nearly painted on? Interesting to see the valve cover pattern from the cam gears. Comforting to know they get enough to throw like that. Did you already clean it (valve cover) above the timing chain, or does the chain not move fast enough to throw oil?
The PO used Penns#%t. I dont remember if the whole cover was that way or not.
There was nasty hard black crud under the plate on the valve cover. I hammered it till I could get as much of it out from under there.Nasty!!!
Generally, sythetics help prevent this type of varnishing. Frankly, it is not going to hurt anything, sludge would, but you don't have that problem. If you really want to get rid of it, there is this stuff called Auto-Rx that the guys on Bobistheoilguy.com are gaga over. They say it will get rid of the varnish. Basically it involves running mineral oil for 500 miles with the stuff, changing it out, and going another 1500 miles and chainging the oil out. Me, I won't touch the stuff. If I wanted to clean it out, Redline with its high ester base which cleans pretty well for a few oil changes.
I'll be interested in what others say on this, but those are likely to be solids that have accumulated on parts from chemical reactions and heat over the years. It represents solids accumulated from the passage of thousands of gallons of oil flow over the years. I would be very wary of using a solvent that would dissolve the stuff back into a solution in a short period of time, as it could start moving around in a semi dissolved state and clog smaller orifices (valve train, etc). Once such an orifice is clogged, there would be no more solvent flow through the orifice to continue dissolving it. A catch 22.
In my opinion, it doesn't do any harm except prevent a bit of heat transfer off the parts that the direct contact of oil would otherwise create. It's not in the bearings or contact surfaces like gear teeth, so really it's just the look.