Open Rockers
There is definitely a certain lure to the older open rocker 4-strokers! Yes, lube the lash point (between the push-rod and rocker arm) and where the push-rod meets the lifters before flights, but not too much oil as to attract unnecessary dirt. I have not run one myself, but I have never heard of any issues with spitting oil. I believe the reason for enclosing the push-rods was two-fold: one, to protect the fragile push-rods from being bent, and two, to provide some lubrication from normal running. These are cool looking engines, and would be right at home in an old-time craft. It would stand out on the flight line! Enjoy!
FP