There are four large plugs that seal in the coolant. Two on the side and one at each end. On my 38 216, the holes were in good shape. I took a wire wheel to them and then used blue thread locker on the plugs. The convex plugs were a very tight fit and I had to be careful to get them without going crooked. Once seated I placed a small flat faced hammer against the plug and hit the hammer with a bigger one. I created just a slight deformation.
