Chorner, You will need to take the engine completely apart to drill and tap the crankcase (timing chest). I am sure drillings and tappings would be destructive to the moving parts! The crankcase is also fuel distribution. The drains would need to be plugged or else they would greatly lean the mixture. Oil is not just added, it is drained to remove the corrosives too. Really, removing tappets is very easy. -Tom