Pictures tell the story.
Burned thru #4:
Large amount of oil in cylinders, primarily #3 and #4:
The culprit, intake manifold machine finish is crappy. Look close at the machining "swirl" marks. The thin rubber around the ports was not sealing and they were sucking oil in at the bottom.
I think I finally found the source of my oil consumption! This also explains why even with a totally different engine, it blew #4 three times. This ported LIM was used on both engines! ot only is the affected cylinder lean, but oil fouled. Oil does NOT compress and it burns hot as hell, both contributing factors in pre-ignition and detonation. I had oil problems on the first engine, too. I also have an idle issue where the IAC is closed and the engine still runs at 850-900rpm. I could NEVER find any external vacuum leaks, so I knew it had to be internal, just never had the time to trace it down.
I am going to have the LIM skim-cut to smooth it out. I'm going to polish the combustion chambers, too, while it is apart. The chamber will receive a radius cut on the affected (blown-out) edge to bring the chamber wall to the edge of the h.g. This will reduce the tendancy to create a hot spot in the chamber. I'll radius back the heart behind the valves, too.
Everyone have a good Christmas! See you back here next week.