I had a local mechanic replace my Valve Cover gaskets about a year ago. Since then I've gotten much more comfortable with wrenching on this beast.
I've been getting a 'hot oil' smell and i think the valve covers drip a tiny bit onto the hot exhaust.
There is one accessible bolt - front passenger side. Oil is dripping from there. I removed it and added a small washer and that seemed to help.

My question, there was no o-ring on the bolt i removed - online it seems all the bolts come with o-rings. It that standard? Did mine never have the o-rings?

 

O-rings not normal. You need tighten the outer bolts, all four are accessible.

 

It's not really an O-ring but the proper bolts do have a rubber sealing thing under the bolt head -- do yours not? I had a D2 that leaked here until I figured out someone had used the incorrect rocker/valve cover bolts.

 

Mine do not have that. Might order and replace the 4 that are easily accessible.

 

That is not factory. Valve covers are not leaking from the under the bolt heads, they are leaking at the rear corner of the covers. You just need to snug down the bolts.