I first polished the fins, then taped them off carefully, trimmed excess with sharp razor, and primed the inside. I then took the tape off, polished again, then taped again, trimmed excess with razor, and painted. After the paint was applied, I still had to polish the fins more just cause that's how I wanted it to be. Blinging, This head is making my engine run really crappy until it gets hot. Once it's hot, it runs good. I have been hearing some stories about these heads destroying peoples engines, but I don't really take mine to the absolute limit, so I hope mine will turn out good. I don't know if this matters, but I ran the billet head from day1, meaning I never ran the stock head onthis engine, and It's being broken- in with the billet head. I hit 39.2 mph today. setup-pk80, Jim's Billet Head, and Intake, stock carb, stock exhaust, 38t sprocket. I'm thinking I need a speed carb, and a chamber pipe next.