Eagle Repair: 83 wagoneer 360 engine, blown head gasket, engine oil pressure


Question
Purchased an 83 wagoneer lately..it seemed to run fine exept for some smoking from exaust during warmup...decided to take it on the interstate and see how it ran at higher speeds...after reaching about 60mph...the softplug at the rear of the engine blew out...i had it replaced...my question is...what would cause this and can i expect it to happen again?...i'm hesitant on testing it again until i can find out if there is some other simple testing that i can do to get more of an idea of the condition of the engine...oil pressure is good...runs cool...no knocks...just would like to know how to tackle this situation...could it be a cracked block or blown head gasket building up pressure in the cooling system?....thanks...Ken

Answer
If it was a coolant loss, it could be a porrly installed plug, or rust that made it pop out (I don't suppose you were able to save it?) This past winter may have been too cold for the amount of antifreeze in it, and it partially pushed out the plug (check the rest are still flush) You can put a pressure tester on the rad to see if there is a buildup, or remove the seal from the old cap and run with the overflow bottle nearly full (being non-pressurized will push some air into the bottle that you will see bubble if it's got a blown headgasket)
  Don't always trust the factory gauges. They can lie both ways (Some carlots have been known to add a resistor to the temp sender and oil pressure wire to ground, so they ALWAYS read good!) I prefer mechanical gauges that don't falter due to voltage changes.
  You probably are lucky, and it's fine though. These motors take an enormous amount of abuse and most times come back from the brink!