Tom, sounds like a good idea. And I don't think a threaded rod is necessary, just a short 5/16" machine bolt.
I grabbed some hardware to test it out.
I put the nut at the top and as the nut is tightened, in theory, the metal would be flattened if the top side washer could bear on the raised area beyond the dished hole.
But in practice, it looks like I'd need something other than a washer. There isn't room for a large enough washer that would bear on the raised top side of the lip. It would need to be a very rigid rectangle that would bridge over the hole so that tightening the nut would pull the hole upwards, flattening the bolt hole area. The washer under the bolt head will bear on the underside of the dished area. I suspect I would need to use a few washers to make it stout enough. That is no issue, just increase the length of the bolt as needed.
But the largest washer that will fit would simply bear on the dished area at the hole on the top side. Clamping down would just squeeze the dished bolt hole area, not move it.
I also wonder if I could torque a 5/16" bolt enough to actually flatten that area.
Assuming the valve cover bolt holes did start life flat with the rest of the lip, I guess the only way the holes got dished was to over-torque the 5/16" bolts. If they didn't snap as the holes dished, I suppose a 5/16" bolt wouldn't snap while flattening the hole area.
But I still would need to machine a suitable "bridge" to apply the clamping pressure in the right place.
I wish I had thought to fix the holes before getting the covers rechromed. It might be a bit easier to flatten the holes if I had no fear of damaging the chrome.
If somebody can think of a standard piece of hardware that could be used to act as the "bridge" across the bolt hole, please chime in.
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