There are big engines, and then there are really, really big engines. In the 1960s Ford and the other large American automakers built some of the largest engines to ever go into production vehicles, and the 429 cubic-inch Boss 429 wasn’t even one of the biggest ones. However, modern technology has allowed motors like this to be punched out to massive specifications, as big as 557 cubic-inches in this particular example. Can you say torque for days?

Unfortunately, all that torque can wreak-havoc on an improperly-built engine, as this next video shows. A stock flywheel just can’t handle all the power of this stroked-out monster motor, which is slated to go into an equally-monstrous Mustang.

The owner of this engine was the one doing the filming, and we can only imagine the shock and horror as he watched his big, expensive engine go boom. He even knew going forward that the stock flywheel, which was used when a billet flywheel wasn’t immediately available, could be a problem. That said, let’s not tarnish the reputation of the flywheel entirely.

The stock unit held up to seven runs prior, blowing up on the eighth. The engine was thankfully rebuilt, and is now in the infamous Boss 557 Mustang, a car disguised as a Boss 429 but packing lots of modern go-fast goodies like a Tremec 5-speed transmission and Heidts front-and -rear tubular suspension bits. It’s a serious engine for a serious Mustang, and by the way, it made 850 crank horsepower before going boom. So our hat is off to that stock flywheel for lasting as long as it did. Lesson learned, right?