Relieving the cases for 80"

When I discovered I needed to replace the flywheels I decided to go from 74" to 80" displacement.  This involves several small operations, most notably buying flywheels with a 3/8" increase in stroke.

As mentioned in previous posts, the piston skirts needed to be shortened by about 0.250" and the heads had to be milled to clear the pistons at TDC.

The other modification involves relieving the cases to clear the rods at the front and back.  Bitmonkey helped me do this gingerly by hand with a file.  We checked it by assembling the pistons on the rods and crank, and then put the cylinders in place on just the right (pinion) side case half.  We ended up taking off about .125" from the front of the front cylinder opening, and the same amount off of the back of the rear cylinder opening.  I was worried about clearing the lip on the cylinder, but it was fine, and we didn't have to relieve between cylinders either:

Once we got the right case half relieved, we simply relieved the left case half to match.

This pic shows how far down the pistons are at B.D.C.   The skirt actually extends about 3/8" below the cylinder, and comes within about .100" of the case.

The final thing I checked was the clearance between the scraper and the flywheels, shown below.  It's supposed to run within about .025" , and I bent it up until I got the clearance right.  Apparently this scraper is a 1947 only feature, intended to make the scavenge pump work better.  In 48 and later, they cast a special channel in the case halves to accomplish the same thing, so I guess it worked!