I second what Doug Stump says above. Whatever you do, don't paint, blue or anything else the radiator. It should be bare aluminum and as clean as you can keep it. Think of air cooled motors with aluminum heads. VW bug, Harley, etc. They were never coated because they radiate best if the bare surface is just kept clean. Polishing is not recommended. When I finally got my Lewis gas system apart (thanks for the help Doug) I was surprised when I found three names scratched into the radiator fins just above the gas tube: J.Myers, D. Myer, and R. Kincade. Each one was done by hand scratching something--probably a bullet or nail--to leave their names. It was difficult to see and impossible to photograph. The thought crossed my mind that this was the crew: One gunner and two helpers. Kind of made the hair on the back of my neck stand up!! Oil on the radiator will bake in but its worth your while to clean it well and install it clean and dry. It's worth the wait, My Lewis took 39 weeks. Fred