Hyperuetectic 3.8 Piston
Federal Mogul/Sealed Power H521AP



Features of Note:
  • This is the Federal Mogul/Sealed Power #H521AP piston with the turbo .245 dish.
  • It has a much shorter skirt than the factory piston.
  • It does not have a full skirt.
  • It has much less support under the piston pin.
  • It does not have the oil drippers from the lower ring to lubricate the piston pin.
  • It does not have the steel support for the top ring.
  • It does have a much higher shine to the machined surfaces.
Features of Note:
  • It has two notches in the top of the piston to show the side installed toward the front of the motor.
  • It has a fully machined top and sides. The GM piston has a cast top.
  • It has oil drain holes from the bottom ring which flow down inside the piston.
  • It would seem that the greatly reduced amount of piston skirt, and thelack of a full skirt design, would allow the piston to rock more in the piston bore than a GM piston.


Features of Note:
  • It does not have the steel support plates on the sides of the piston around the piston pins.
  • It has visibly less material around the piston pin.
  • It has additional support ribs cast from the piston pin to the top and sides of the piston.
  • It has a single oil hole drilled from between one pair of the support ribs into the piston pin bore. The one in this picture is just visible at about the 10 oclock position inside the hole.

Submitted by:

David Chase