Sorry, I don't agree. Bigger exhaust will do little to nothing for a stock engine, and be expensive for the small if any gain. Porting will help upper RPM, not much gain below 3,000 rpm. I do agree on the electronic dist with a recurve.
As for milling the head, why .050 for the 170, and .100 for a 225? That does not tell you what CR. Need to take measurments and determine how much to mill to get the desired CR. Milling the 170 .050 will really only gain a small amount of CR, as the first approx .020 will only make up for the difference in head gasket thickness, of the factory stamped steel gasket and the aftermarket composition gasket.
