http://4ac-powered.forumotion.com/block-lower-end-f10/-t1.htm Read only, if you want to add something or have input on existing information PM the Admin Sun, 26 Apr 2009 21:31:31 GMT 10 http://i87.servimg.com/u/f87/13/77/65/79/4ac_po12.jpg http://4ac-powered.forumotion.com/block-lower-end-f10/-t1.htm http://4ac-powered.forumotion.com/block-lower-end-f10/piston-specs-t26.htm NP75 The stock 4AC pistons are cast aluminum units. The basic size specs: Diameter – 81mm Wrist Pin – 18mm Compression Height – 30.5mm Compression height is the distance from the center of the wrist pin bore to the top of the piston. The piston is dished, meaning that there is cavity in the top of piston. This cavity is approximately 10cc in volume. Stock Piston weights: Piston with no rings – 270.8grams Piston with rings – 295.7 grams Wrist pin ... Block & Lower End Sun, 26 Apr 2009 21:31:31 GMT http://4ac-powered.forumotion.com/block-lower-end-f10/piston-specs-t26.htm#100 http://4ac-powered.forumotion.com/block-lower-end-f10/piston-specs-t26.htm http://4ac-powered.forumotion.com/block-lower-end-f10/flywheel-specs-t25.htm NP75 The flywheel is one the ugliest parts in the 4AC from a performance point of view. It is a steel or iron part, it could be either cast or forged. Most likely it is an iron casting. It is a behemoth. It has 6 bolts fastening it to the crankshaft versus the 8 used on the 4AGE version. This means that it won’t have as much power transmitting capacity, but I am not aware of any failures in this area. The pictured example weighs approximately 21 pounds, the Club4AG tech reference lists ... Block & Lower End Sun, 26 Apr 2009 20:49:15 GMT http://4ac-powered.forumotion.com/block-lower-end-f10/flywheel-specs-t25.htm#99 http://4ac-powered.forumotion.com/block-lower-end-f10/flywheel-specs-t25.htm