When an engine wants a lot of timing its lean. When you have low comp and a bigger cam there isn't a lot vaporization taking place before ignition time so burn proceeds slowing.
You can turn this to your advantage by saying ;
If your engine will accept an increase in timing, then you might simultaneously be able to lean it out.
That is partly how I got 32 mpgs(hiway) out of a 223/110 cam. The other part was bringing the rpm way down to; 85=2040/65=1560. Of course the 180 plus psi cylinder pressure probably had something to do with that as well.
