missing drain tube between head and block

[seniorchristo]

Great explanation mini! Thanks all for the discussion
Chris

[rgh0]

The rubber tube is not actually a drain tube but as others have said a connecting tube from the block vent up to the vent chamber lotus put in their heads. the hole in the side of the head, on the side of this chamber, is then often connected to the airbox or left to vent to the ground via a hose. This head chamber is not connected to the cam area. .

There is actually also a connection hole in the top of the vent chamber into the head cam area as well as the vent tube from the crank case in the bottom. The rubber tube in good Chapman fashion serves both a vent tube and as an oil drain back to the sump for any oil that collects in the chamber.

Without the drain tube old oil will collect in the chamber through the top vent hole into the cam area. You should plug the top hole in the head if you are going to decommission the chamber and leave it open at the bottom so it is not totally enclosed and free to drain.

cheers
Rohan