Thanks for the info.
Its funny you mention glazed bores - its not something I have heard of so much in the last 10 years, I suspected this is the sort of problem that would have gone due to modern fuels or lubes. Presumably your engines don't have chromed bores (or Nikasil, or whatever they call it).
As regards overheating I was thinking of a little extra local friction and close tolerances maybe heating and hurting something, such as a plain bearing or a piston.
Would like to put my V8 Landy on a dyno one day - not sure how they do this on a 4x4. We have chassis dynos where I work, but for 2WD cars. I don't suppose they would let me play with one though. I am just switching to fully mappable ignition (I use a Holley Commander ECU for the EFI, now adding MSD sparks), it would be great trying to optimise an ignition map on a dyno, in fact it might be tricky without - but it will be fun trying.
Steve