Yes, it has to be a blockage somewhere in the water jacket. Hoses and radiator are fine.

What's the best to way to find the blockage and remove it? No sludge or gunk comes out when flushed with water in both directions.

When pump was off, I blasted water from the front of the engine and through the petcock to the front.

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)