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20-Dec-99 Block Prep Part 2

Decking and Cylinder Honing



ImageThe block was then cut with the CBN cutter. This is not actually a grinding wheel but carbon cutter, there is a difference. Grinding wheels tend to give away as your cutting, leading to imperfect cut. The CBN cutter cuts accurately every time.
ImageAfter they make the final pass the bolt holes are chamfered to make it easier to start the bolts, and to eliminate any areas with sharp edges that could cause the head to torque incorrectly or give the block a place to crack.
ImageHere it is after decking…. isn't it pretty. The block is in bear metal at this point.
ImageNext we bore and hone the cylinders. Before we bore the block each piston is checked with a micrometer. Every piece that goes into the motor should be checked before assembly. Never take for granted that every piece is to spec just because its new. This can eliminate a great deal of work in the future tearing down the motor to find out why it won't run right.
ImageThe block sits on the mains instead of off the existing deck for greater accuracy. This is an exact 90 degree fixture that bores the holes perfectly inline to the crank center and the deck center line.
ImageThe holes are now bored and the tops are chamfered. We bored to leave about.0052” left to hone because when the cylinders are bored the metal is actually torn. The boring bar cuts but if you look closely it is microscopically tearing the cast iron. When you hear the horror stories of engines that the rings never seated in, there's a good chance that the cylinder walls were not honed to the proper finish and some of the cylinder wall tearing was still present, or they were honed too much and were too polished to seat the rings.