Dart Big-M Block Machined Upgrade - Scratching The Surface

There's no pretty way about it: The lifter bushings must be pressed in using a driver and a hammer. Dominguez placed each bushing in its bore (tapered side down) and drove each bushing into the bore, all the while making sure not to drive them in too deep.

Dominguez checked his work, ensuring that each bushing is pressed in properly; too far or not enough can cause lifter failure.

Out of the box, the CHE bushings needed to be bored to 0.904 inches in order for our lifters to fit. Dominguez first drilled through the oil galleys of each lifter bushing, which feeds oil to the lifters, and then he prepared to set the block back onto the CNC machine.

Lagman measured the lifter bushings and programmed the CNC to begin removing material. The CHE bushings' inside diameter measured 0.902 inch, requiring a final finish bore for the additional 0.001.

The bore honing process could begin by using a torque-plate that was torqued to 65 ft-lb, in oreder to simulate the cylinder wall stress of an actual cylinder head. Without this plate, false cylinder bore readings can be had. Depending on your shop of choice, bore-honing a block with a torque plate could run around $200.

Lagman measured the low-compression pistons and took into account piston ring clearance. Before the block was honed, it measured 4.525 inches, and to get proper ring seal, an additional 0.005 inch would have to be removed by honing. Bore honing will also give us the crosshatch pattern we desire, and the pattern will retain a film of oil on the walls of each cylinder.

From here, our Dart Big-M block was ready for a thorough cleaning and paint. Expect to shell out another Benjamin for a general detail job.