**Milling .030 off '920 - 273 heads**

I agree, compression is one of the most expensive with little pay back per HP with in itself. Most street engines are some where between 8:1-10:1 and going from the 8:1 to 10:1 will only give you 8-10% power increase. Cam and head flow are where the majority of the power is. I'd only worry about getting enough or close enough CR that your cam requires, so unless your going for a larger cam and or porting your heads I wouldn't worry about trying to bump you CR through milling your heads.