Okay, a lot of things going on here... I just pulled the stock L98 heads off of my rebuilt L98 engine ultimately because it would overheat very quickly. Between a compression test, leak-down test, and posting back here, I'm thinking that my heads might be cracked or that I have cracked valve seats (see here for the results of those tests).

Anyway, one of the things that I noticed several weeks ago when I first pulled the plugs out was that many of them (especially those on the passenger's side) were "wet" with what I believe to be oil. After I pulled the heads, some pistons looked more "wet" than others (they had a sort of shine to them being covered in oil).

One of the things that I'm trying to rule out is wether or not the oil is getting there through the rings. My guess is that, in order for oil to get past the rings, the engine must be running at a good enough speed to get the oil up there--and if it's running, it must be hot--and if it's hot, the oil should burn off--and if there's oil on the pistons *now*, than it must not have got there when the engine was running. Follow me? So, then, is this just a case of worn valve guides? (These heads were "rebuilt", which I assume means new valve guides--did my machine shop screw me? Seems like a hard thing to screw up for an experienced machine shop.)

I have pictures of the block and the heads...

 

DRIVER'S SIDE BLOCK

 

DRIVER'S SIDE HEAD

 

PASSENGER'S SIDE BLOCK

 

PASSENGER'S SIDE HEAD