That started in 1960. We are talking pre s/n 50662 here.Fresh air comes from an operable scoop on the side of the fuselage. The heat box allows warm air in or if closed it dumps that warm air into the cowl.
Breakpoint was either 50662 (1960) or 50912 ('61), off the top of my head. Need to look in IPC. Regardless, still curious what a 'seaplane mount' is on an early 180 with the "old style" cabin heat valve assy.180_jeff are you sure that that fresh air scoop started in 1960? I could get one and stick it in if needed.
OK I FOUND ONE!! Found a 180C with a virgin looking firewall. No fresh air vent on the cowling side. The combined fresh air/warm air diverter will fit to the inside of the vertical tube. It is tight but does fit. Thanks for the input.
DENNY