The Stovebolt Site Forums The Shop Area Engine Shop clogged 6 cyl engine coolant drain plug

At least two plugs on manifold side - not easy to work around the exhaust manifold/pipes

At least one at the rear of the block - blocked by firewall (this/these are critical for a good clean interior

maybe one at front of block? - if so, it may be accessible

The earlier (1955nd and earlier) water pump can be removed to get at those holes in the front of the block - these are very small holes compared to 1955 and later blocks (with the water pump in the "wrong" position for good radiator cooling.