Kirpich

When a car overheats bad, it may warp the head and that's how the coolant got into the oil, through passages. Coolant in oil + driving for a week = bad times in the crankcase. So a rod seized up and broke, even though head was redone.

fatjoe10

When the radiator first failed and overheated the car, the damage was most likely already done (head gasket blown). However, having him drive the car around with a blown head gasket was a poor choice/advice. No car should be driven for a week in such state. The smoke coming out the tailpipe right after the rad was replaced was the first sign to stop driving the car.....

wadzii

there are 2 things that could have happened.

1. and the most likely. coolant was mixed with the oil while the hg was blown, coolant dosnt lubricate well. The rod seized on the crank and broke when it was started up.

2. while the hg was blown he hydrolocked the motor, the rod finally broke.

JDR159

He may have warped the block, not the head. Aluminum block engines can warp if they're overheated enough. This should be checked when rebuilding the engine...

viets2000

main and rod bearings being lubricated with a coolant/oil mixture for a week. Not a good thing in my book.