What not to do when working on a car...
 

Hmmm...

http://www.thetartcart.com/videos/watch.aspx?Media=1911

I think he blew the headgasket.

Wow that guy was lucky. Top fuel drag cars do that to. Although with them very often the block itself is in many many parts.

Probably back fired, wonder what kind of fuel they were running? Bet it wasn't gas.

I saw the same thing on a pulling tractor some years ago. The guy I saw had a GMC style blower and hilborm fuel injection. He feathered the throttle which reduced the air intake, but the injectors kept dumping the same amount of fuel. When the throttle opened up and all that air hit the vaporized fuel, it blew both heads and the manifold off the engine.
I can't tell if it was the same scenario, or not.
Glad my hand wasn't on the manifold when it blew...

reason why they have shrapnel blankets on the super chargers