Glenn,
I'm not sure where I was leading on my post. If the rocker were to seize to the shaft and break the rocker arm, it would be 'permanent and stationary'...you wouldn't have to hunt for the problem. I drove a 235 from San Diego to Arcata, which is almost 900 miles, with nary a drop of oil to the top end. It made noise and ran weird, but it never broke anything.
I was thinking more in terms of lifters going flat or instantly pumping up and affecting the rockers. This thinking is marginal too! The ONLY thing the intakes have in common is they are much lower (higher?) in the combustion chamber than the exhaust...nearer the piston!
The two pregnant questions are, why don't the fragile pushrods bend first, and if it is a valve/piston contact issue, why doesn't the valve bend, or the internals show evidence of contact.
The oiling system is large and feeds not only the cam bearings and lifter galley, but also the mains. These things won't run without lube. I think the passage is plugged just inside where the fitting screws in. Keep looking and let us know.
Stuart
