Back in the 70's when there was a shortage of parts for a while we had a machine man bore out the towers (with caps bolted on) then he made half round bronze "shells" (about 3mm thick) that he stopped rotating using a hardened steel pin through the shell into the alloy.
This meant that as long as the cam lobes were OK he could grind the bearing areas round again and make "shells" to suit whatever.
Used to cost about 75% of buying new parts but we did it cos the parts were on 12-15 week backorder at the time
I have a similar plan, Bryan: today, a mill can "circinterp" (circular interpolate) a half-round hole on just one side, so I won't have to pin the bearing against rotation. I can just install a bearing (possibly a flanged bearing) in the cam tower half and use the matching cap above to capture it. I'm hoping to use common bearing inserts, if I can find the right size, but you do bring up a very good point: many of these cams have journals that are either worn some, or were simply out of spec (from the factory, very common) on the small side. The ones that came out small were the ones that wore fastest (this was mostly in the K4-K6 engines) because they could not capture the oil film for too large clearances.
So, bronze is an excellent idea! And easier to make than plain inserts might be to find...it withstands poor oiling conditions better, too. I'll be looking at that: I might need to use a mill to finish-size the bearing in place, which would be a cost increase, though.
There's always the babbett bearing approach, but it's been some many years since I used it, I'm not sure I remember how to do it for small ones like this: it's a sort of "solder fill" bearing technique where you can make a perfect bearing fit to a journal, so the oil pressure makes for a perfect film, lasts forever. It requires a break-in time of lowered RPM, which is why carmakers dropped it in the 1950s for common shell types instead: if you ran an engine too fast, too soon, the babbett bearings would burn and fail. If you waited 1000-2000 miles first, they outlasted the car. The upper speed limit, in these cams, would be 5000 RPM at the cam, so it could work...
