my newly rebuilt engine on my M38A1 blew out the freeze plug on the back side of the engine. I went to get new freeze plug at auto part store and was told the one that came out (I found it on the road.) was installed backwards it is a small metal concave disk it was installed with the curve to the outside. does anyone know the correct way to install them all of my were installed the same way at the Machine shop. I know this sounds like a dumb thing to ask but just something I can't find an answer to and I have never installed one.
The flat style or flangeless freeze plugs the curve faces outward so when you strike the center of the curve with a hammer and punch the disc expands and tightens itself in the hole. If the center area of the curve is not dented significantly then it may loosen and fall out.
Here you see many sizes of the flange type with several different flange sizes. The flat disc lower left is the type installed with bulge outward and peened to expand after installarion.
The flange type if not dimpled in the center should be installed with a proper tool that fills the area of the plug inside the flange since the forced flange does the sealing.
Flange type
An alternative tool to sub for the bushing driver tools.
my newly rebuilt engine on my M38A1 blew out the freeze plug on the back side of the engine. I went to get new freeze plug at auto part store and was told the one that came out (I found it on the road.) was installed backwards it is a small metal concave disk it was installed with the curve to the outside. does anyone know the correct way to install them all of my were installed the same way at the Machine shop. I know this sounds like a dumb thing to ask but just something I can't find an answer to and I have never installed one. 
