I support Richard (42guy), plug it. There is a small (.060) hole in the pushrod hole that allows pressurized oil to enter and lube the pushrod and the rear cam bearing. That is why the little umbrella is on the rod, to keep oil from spraying up. Now with the rod removed, the oil from the hole can flow more freely and might slighty lower oil pressure. I have read but not seen that if the hole is not plugged some misting of oil may show up on the firewall. Not sure how it could get thru the oil filler cap. jmo
John
Richard, did you get a chance to get to Saratoga?