Yeah 318 valves are not for amateurs. But I think Mike Jeffrey sets up his heads with longer valves, you might call and ask him what he does. The problem with the stock length valves is you can't get much more than .500 lift, which is cool for me but the big power guys might not like that limit. Not sure how much lift you can get before you run into rocker geometry issues though. Beehive springs would help with that.