hello; the afr 165's flow slightly more than the eddys but as i mentioned, that is irrelevant. parts must be matched. i forgot why the eddys are cheaper. i know the springs are not quite as good but they don't need to be for a small cam. air flow at different lift is what needs to be matched to a cam. the cam must be matched to compression and gearing. you could have irom heads or plastic heads or papermache heads. if the all have the same air flow and chamber size they are all capab;e of producing the same hp. afr's are great heads, buy them if you want them. the have 58 cc chambers so milling them .036" will be much better than milling the eddys .036". they also have the 1.9 and 1.6 valves like the smaller eddy's.