Until you put a cam in it, anything does little. But it does add up.
All I do on Briggs 5hp is to take the edge off between the valves and the cylinder.
Take a sharpie and a head gasket. Set the gasket on the block and mark the area the gasket does not cover between the valves and the cylinder. I then take a sanding roll and smooth the lip(eyebrow) by the valve so it is more like a gentle ramp towards the cylinder.
Some people will take the block down to where that edge is even from valve to where the upper ring stops. I think that is too far, but everyone has an opinion.
I don't like taking out a lot as all the metal you sand away lowers compression.
The exhaust side is less important in the eyebrow area as the gasses are being pushed out, but the intake side should be smooth.
Sometimes I think people forget the exhaust is under pressure and the flow is not the same as when under vacuum, ie: less than atmospheric.