If you look at a 216 after a long highway run, you will see fumes wafting from the vents in the valve cover at idle or after shutdown. These are fumes coming from the crankcase. Since the draft tube does nothing at idle, the vents are there to let it out.

Last edited by 52Carl; 02/19/2018 1:30 AM.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission