After running my Perkins 6.3544 NA for several hours there is a thin oil vapor
film on top, near what looks like a breather or PVC type cap.  Should cap be
replaced or is this fine film normal?  Bob Siegel 36'MT sundeck "Shalom"
Annapolis

Don't know about the Perkins Bob but my Ford Lehman has a breather type
fixture on top of the rocker arm cover. Attached to it is a 1/2" OD tube
that leads down to the intake air filter. It enables the oil vapor from
inside the "cover" to be drawn into the engine with the incoming air.
Perhaps you need one.

Jerry & Barb O'Neill
GB 32 ADVENTURE
Annapolis MD