Cruzin I was running down I44 in my 1989 Chevy 1 ton puling a 3 horse horse trailer running around 70--the big 454 kinda backfired and then started making a really not good sound.
long story short the head gasket blew
filled the #8 cyliner with antifreeze(that was out best guess since it actually blew out a big chunk of the gasket in that area) and exact ally what you said happened the water could not compress fast enough so the pressure actually snapped the steel crank it still had #6-#7-#8 attached and it would actually turn over just would not start