Lost Frost plugs
At your request.. lol
If there was water, why didn't the ice go up instead of forcing the plugs out..
I realize that it is now a moot point but I like to understand the whys....
IIRC Water freezed from the surface down,, the frozen surface forms a dam,, the rest of the water can't push up,, so it pushes out..
I've had to replace dozens of popped frost plugs,, from both auto and marine, (some people think saltwater cooled engines won't freeze,, they do)..
We never pulled every engine because it wasn't practical, cuz you'd get a dozen or more at a time.. I would estimate 85% of the engines we just replaced the popped plugs, then visually or "feel" check the others, replacing as nec., then pressure test the cooling system,, they survived and lived for many years,, the others,, would have evident probs as described in the very first posts..
Folks around here, weren't always as diligent about antifreeze when these cars came out.. and we seldom get below zero weather for more than 3 or 4 days
my .02,,
replace the frost plugs
fill with water,, check for water in oil, spin the engine with sp plugs out.
install plugs and fire it up.
cross your fingers..
if it's cracked your gonna find water somewhere
if it's not,, good karma man..
hope it helps
PS,, after running it,, take the sp plugs out,, wait till it's time to refire,, then spin it, hoping for no water..
It would be a good idea to drain and save the the oil,, leave the drain plug out,, with a container to catch any water, if it's gonna leak..