With the four blocks cast, our attention now turned to the next hurdle, which was facing and boring the blocks. We knew from the outset of the project that the boring of the blocks would be a problem, as there were no local facilities available to us.
 Facing the blocks
Facing the blocks The main issue was the length, which required boring, which was over 1 meter and 127 mm in diameter. We initially tried a number of local engineering companies without success. In our search we found a local company which had a horizontal borer capable of facing the top and bottom and the chest face of the blocks. This required us to make a frame to hold the block in a horizontal position. With all four blocks faced we now proceeded to tackle the job of boring the blocks. We had been thinking about how to complete this task for some time and finally we decided to complete this job ourselves.  Length of the boring bar
Length of the boring bar We had two 65 mm bearings available to us, so we purchased a 3 metre length of mild steel bright bar to fit the bearings, unfortunately when the bar arrived, it had been strapped to the back of the lorry and had acquired a significant bend. We straighten it out as much as possible in a press, but it still had 0.008” bow in the bar. I  Boring the blocks
Boring the blocks Surprising this would later work to our advantage when we started boring. The frame was now adapted to hold the bearings and boring bar. A motor gearbox unit was fixed to the end of the bar, controlled by a variable speed inverter. A small jockey wheel was fixed to the motor gear box to guide the bar along the floor. We purchased a 3 metre length of threaded bar as a feed screw. Two gear boxes were linked together to turn the feed-screw, again controlled by an inverter.  Finished boring
Finished boring By using a clamp on tool holder we could remove the holder regrind the tool and with the use of a DTI could calculate the amount of cut we were applying. The framework was then bolted to Dave’s garage floor and boring commenced. We had allowed 10mm to be machined out of the bore, in retrospect, we probably could have got away with half this amount. It turned out we could only take out about 0.010” cut at a time, and each cut took approximately 1 hour to complete. So each block in the end took around 28 hours to complete. The upside was that it was extremely low cost. The bearings were adjustable in vertical and horizontal axis. A DTI was fixed to the bar and the top and bottom faces were clocked in. The bearings were adjusted until the boring bar was true to these faces.  Drilling and tapping
Drilling and tapping T he bores were coming out small in the middle due to tool push off in the unsupported areas. Now the bow in the bar came to our advantage, as we moved the clamp on the boring head to the high part of the bar and by taking small cuts the worst bore came out with a 0.003” variation and the best was within 0.001”. The blocks were then moved to Wayne’s shed for honing. This task was completed with a modified cylinder hone in a pistol drill. This was a slow and laborious task taking several hours each, not to mention dirty. The pistol was pushed beyond its design limits.  Finished bore
Finished bore In the next part we will cover the manufacture of the smaller components of the engine. To read “Part 1 - Measuring up the original. Main block pattern making and core building. Casting the blocks” of this project please click on the link in the keft hand column of this page.
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