[ted]

427 and 428 dampers are all factory zero balanced as is the case for the other car Fe's, 410 Mercury included. Only the 428 SCJ was external balanced at the front of the engine and was done so with the cookie cutter (ax head) sleeve behind the damper.

The standard 428's, CJ's, and 410's were external balanced only at the flywheel as they had an additional counterweight on the 1U and 1UB cranks allowing the damper end to remain at zero balance. The 428 SCJ had the 1UA crank which was missing that additional counterweight and needed the extra weight or rotating mass at the front of the engine.