Here is my latest lifter galley cover with an O-ring to make the seal. The implementation of the roller valvetrain forced this cover to be somewhat simplified from the previous version (see left side). The previous cover had a set of spray fingers that bounced oil off the camshaft to lube the lifters. While they would have been nice to keep, the lifter link bar prohibited their use. As a result, through the block you see, oil is supplied to the roller rocker spray bar on the head to lube the rockers. The large hole is a crankcase vent that gets connected to an overflow tank. The O-ring has proven to be very functional and 100% leak free.