Years ago, when I first saw the Jim's fixture for supporting a cone style cam cover, my thought ran something like this, "Okay, I see the point, but I sure can't see spending that much for something I've gotten by without for all these years." Nevertheless, the idea is a good one. Support the cam cover in such a way that the outside surface won't be at risk of being marred, along with providing a stable base for installing bushings and pinning them to prevent possible rotation. But face it, the portion of the cover that is filled by the timer cover is horizontal to the gasket surface, so drilling for the pins can be accomplished on a drill press without too much trouble. Just a matter of protecting the finish on the cover. The pinion bushing is a little more dicey due to being off to the side, but one can get by.
However, over the course of time one of my colleagues mentioned that he had one of the Jim"s fixtures and was impressed with how much easier it made the job. Of course his input didn't suddenly transform me from being a cheapskate, so rather than ponying up the money for the Jim's fixture, I made my own, as seen below.
You may notice that mine is a little simpler to fabricate than the Jim"s tool because it supports the cover from the deepest part of the timer cavity rather than the "points cover" gasket surface. This makes the diameter of the pipe of little importance as long as it will fit inside the cover. And my colleague was absolutely correct about how handy such a fixture is.
In fact, I was impressed enough that I decided a similar fixture would be in order for generator style cam covers, especially given the number of early motors that seem to find their way to me. A fixture for a generator cover, however is a little less straight forward, though actually easier to build. At first glance the obvious problem is that there is no flat surface on the outside of a generator cam cover to work from. However, there are points on the outside of the cover that will provide a "level" surface; 12 of them as a matter of fact.
That's right, the mounting screw holes. "But they are countersunk," you say. Not really a problem. It just so happens that the top of a 1/4" acorn nut has just about the right shape to fit the countersink taper which the covers have for each mounting screw.
Having fabricated one of these for doing Big Twin cam covers some time ago, I found it even more essential than the one for cone style cover bushings. So last week when I found myself in need of one for a 45" cover, I snapped a few pictures of the finished fixture.
I used 1/4 inch aluminum plate for the base, since I had some. You probably wouldn't want to use too much thinner material because you will probably want to use countersunk screws so the bottom remains flat. 2" long hardware store screws (more likely to be available with threads the whole length) provide enough depth for clearance on the rather thick 45" cover. Shorter screws would be in order for a Big Twin fixture. The crude drawing is a must to aid in placing the cover onto the fixture without trying each combination of holes every time. Well, ...I guess its not a must that the drawing be crude; just that there be a drawing. I suppose if you wanted to use up a bunch of extra material you could make the support plate the full size of the cover and add more screws so the orientaion would become obvious, but I think I may have already mentioned that I am a cheapskate.
There you go. An easy way to not only protect the finish on your cam cover, but also to hold it level for bushing replacement and drilling for those pesky pins.