hi dave, i just bought the tall valve covers from eddie marine and i didnt have them drill the holes for pvc and the air breather ( i should have), i can find a machine shop to do the drilling but what about the small raised alum around the drilled whole that is on my current covers are they nesscessary for a good seal with the rubber gaskets,also should both covers have an air breather or is one ok. i have heard that you should have two one on each cover (i dont no if that is true or not) i guess im not sure what to do after i got these and i just want a good seal so oil wont leak around the whole that gets drilled, thanks for your info rick