Camshaft question

Hysteric,
It may well need 40*...or more at idle. I have run 53* at idle on a drag car, my street driver runs 48* & a BB Chev reqd 55*.
When you increase idle timing by turning the dist with the engine idling, & the rpm increases, that increase is because the engine is making more hp.
You have defeated your own argument with 'lean mixtures burn slow'. They sure do!
And that is exactly the reason long duration/high overlap cams need more idle timing because the mixture is lean, diluted with exh gas. Same with low CR. More residual combustion chamber space, more dilution, needs more timing. It is simply the nature of the beast.....