I took my 1915 touring on the HCCA tour this weekend. On Saturday about ten miles out I noticed a skip and loss of power. Stopped, checked coils, plugs and timer to see why number four cylinder was not firing. After a bit, it seemed to recover but I soon realized the loss of power and the temp went up. Decided to call it a day. When I got home I took the head off fearing a burned valve but instead found that the head gasket was blown between number 3 and 4 cylinder. Being between two cylinders explains why I didn't see loss of water or steam but why didn't number 3 cylinder show a loss of firing?
I've had blown gaskets between cylinders act like a check valve.