92 Roadmaster Engine Knocking

My Roadmaster wasn't driven for approximately six months. During this time, I would crank it approximately every four weeks and let it run for twenty minutes or so. She always ran fine. Now I'm finally getting ready to put her back in daily use, but the engine has developed a horrible knock that wasn't there before.

I have 45 psi at cold idle (approximately 1000 rpm). Due to the speed of the knock, I assumed it was a valve tapping.

I pulled my valve covers and verified that all of the pushrods were oiling. Prior to this car, all of my experience with Chevrolet small blocks have been pre 1980. Running an older 350 without valve covers would spray you, your fenders, your driveway, and your neighbor's driveway with hot oil! I saw a small trickle of oil flowing over the rocker arms. It's my understanding that roller cam motors don't oil the top end as much as non-rollers, but I ran this thing for five minutes and no oil ever splattered off the heads. How much oil should those pushrods be pumping?

I adjusted the valves with the engine off, per the service manual, without any luck. I tried to adjust them with the engine running (back off until it taps, then tighten just to silence plus one turn) - the racket is still there. Apparently the problem is before the rocker arms.

The knock does not get louder under a load. I let the engine warm up to 180 degrees, but it never got any quiter. I obviously haven't worked with roller cams before. Could a bad lifter possibly cause this? If I pull my lifters, is there anything specific I should look for?

I apologize for this horribly long post, but I wanted to provide as much food for thought as possible.

Thanks,