Stony,
I rebuilt a 1950 Allis Chalmers "B" engine some years ago, and it indeed used peel-able shims to shim the rod and main bearing caps to "tune" appropriate gaps. There was a formula on how much to sand down the bearing shells to accommodate the ultimate height of your shim stack. The shims were brass too.
But, the Jeep manual says DO NOT shim the Willys engine! So I'm inclined to follow orders!
And indeed, here's my update to my "low oil pressure with a very liight knock" situation:
I took the engine out since I planned on replacing the mains and connecting rod bearings.
While worn, all the old bearings looked okay and I planned on just replacing all the bearings. The idea of that noise though convinced me to pop out the pistons. What I found was all the pistons had shattered top rings. They came out in many many pieces. In fact, piston 4 managed to wedge 3 pieces on top of each other in the ring land. So the pistons are no good. Sigh. Remarkably, the cylinder walls don't look like they suffered much from that issue. So I think the noise I was hearing was broken piston rings. Lots and lots of bitty bits knocking about.
Next, the valves were a bit noisy sometimes and here I found that the exhaust valves had about 0.060" side to side slop. Hard to believe this engine ran so well.
It gets worse though:
While inspecting the cylinder wall ridges, I found a 1 inch long crack at the top of cylinder 4. It runs along horizontally above where the rings move up and down. I believe this is the source of my very slight coolant leak.
Dang.
I emailed Brian Hainer (metalshaper on youtube) and I've got an appointment next week to bring the block to him. He says he can help. (He's an hour from me)
My "hobby" budget is very small. We'll see how it goes.
Not sure how much a combo of lock n stitch and sleeve-ing would be.
