AMF Shovelhead Lowrider Restoration -18 - Cylinder Bore / Piston Measure & Ring Gap

Continuing onward to part 18 in the series, we reach the point where work will be conducted with the cylinders, pistons and rings. As such all Items will need to be measured to ensure proper fitment. First however, the missing base stud will need to be addressed, giving adequate time to dry in the block.

I was able to order the base stud from my local Harley dealership PN: 16837-78, it is an interference fit, so installation will not be too pleasant, or, shouldn't be, anyway. I went to Lowes to pick up some 7/16-20 nuts for this task at Lowes. Lowes does not carry 7/16-20 nuts. Home Depot does....

A double nut technique was employed to tighten the stud into the block after measuring the existing studs to determine depth. Also, Ive oiled the flywheel and cut some paper that was oiled and allowed to be rolled a bit into the engine just to cover the hole for the stud to catch any crap from the process. Loctite 271 is used in this process, turning and rechecking with the calipers until the depth is reached. Then the paper pulled out, the nuts removed from the stud, and one final caliper check before its left to dry.

Back inside the house, the cylinder bore will be measured. starting with the calibration of the micrometer. 3.498 + .020 = 3.518 Will be our measurement value. With this set up the bore gauge is then referenced against it. A diagram of how the measurements will be taken is drawn recording the data as taken. Prepping the bore by cleaning it out with a light oil.

Next will be the pistons to cylinder clearance. The manual calls out .002 to .0025 clearance. I used two different methods at the skirt as the vendor provided no info, one comparative, and the other using a feeler gauge method.

After this the ring gap is checked to their respective cylinder, one at a time, as its manually compressed into the cylinder and guided by the piston into the measuring position. With gaps of .017 and around .0025 clearance with accurate bore sized it looks like everything sizes good for the next steps of the project.


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