Now I take the previously measured main housing bore of 2.442”, divide it in half and we have 1.221”. Now add cylinder #1’s measured 7.015” to 1.221” and we have a deck height of 8.236” on the side of the block that cylinders 1-4 reside and 8.227” for 5-8. More than likely the readings at the other end of the block would be slightly different from the factory but not enough to matter in this case because I will use the measured ends as my point of origin and I’m gonna mill a crap load off anyway.
Now that I know what the current deck height is I need to calculate my desired deck height. I want to end up with a “zero” DH when I’m done in order to get to my desired 13:1 compression ratio. The way to figure the desired DH is to add half the crank stroke (3.400”divided by 2 =1.700”) to the Ohio connecting rods center to center length of 5.400” and the wrist pin height of the KB pistons (1.090”). We end up with 8.190”. So, I need to machine a whopping .046” from the block on the #1-4 side and .037” from the #5-8 side to get a “zero” DH. Yes, that’s a LOT! I will definitely have to machine the intake manifold for proper fit and I’ll cover that next month. Off to the surfacing machine we go!
 Here the block is being "decked" to the proper height parallel to the mains. |
 This is the block securely clamped to the underside of the boring stand plate. This assures the bores are perpindicular to the deck. |
I don’t have a fancy CNC machine but I do have a very sturdy, built tough, (and heavier than a brick **** house) machine that does a very nice job of it’s intended function. It removes material and makes “things” flat. It has basically been the industry standard forever until all the CNC stuff started showing up and uses a single cutter bit made of a CBN material that removes cast iron like a hot knife thru butter. The objective of surfacing the block is to obtain the desired DH and have the deck be flat and parallel to the mains. It also needs to leave the appropriate surface finish depending on the type of gasket to be used. So the block basically sits on a precision bar that runs the length of the block and nestles into the main saddles. A clamp holds the block securely to keep it from moving and it’s ready to go.
After touching off of the end of the block that I previously measured I started taking .005” cuts until the last cut on each side which is a .001” finishing cut. By spinning the cutting wheel at a high rpm and slowing down the cross feed rate I achieved a very smooth surface finish which would be appropriate for the newer multi-layer steel head gaskets that are becoming more popular by the day. I am going “old school” however and will use copper head gaskets with a
stainless steel o-ring imbedded in the block. More on that later. I finished up by using a chamfering bit in a drill to re-chamfer the head bolt holes and a small round file to knock off any sharp edges. Now that the block deck height is where I want it it’s time to bore the block. It is a fairly mundane operation, boring if you will. The block gets clamped to the underside of the precision ground plate of the boring stand so that there is a guarantee that the newly bored holes are perpendicular to the deck surface. This is why I decked the block first.
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