A stock 6.0L engine has a 3.622-inch stroke. With a stock 4.00-inch bore that equals 366 ci, for those who don’t speak metric. That’s pretty cool, but we wanted something bigger. We’ve already built 408s before, using 4.00-inch stroke cranks, so we decided to go even bigger to a 4.125-inch stroke. That, plus an additional overbore to 4.060-inch, will give us 427 ci.