Did you happen to drill a 1/8" hole in the thermostat before installing it? Since there is no bypass hose on the 216, the hole helps to allow air bubbles to escape to the radiator before the thermostat opens.
I found that recommendation here.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
