These jig bored engine mounts locate the concentrically ground (inside & outside) full hard (O-1 tool steel) front ends at the correct gear locations. The three holes are bored to the same size as the ground front ends, at the same time, in the same setup, insuring squareness in both axes at the same time. The front ends are easily slipped into these holes because of the two jack screws located between the four flat head clamp screws seen in the top photo. The eight visible through holes which allow fastening of the front ends, the crankcases & mount together, plus the four clamp screws, give one very rigid unit when all the alloy steel screws are tightened to 50 in lbs of torque.
