At this point in my engine career, I will not repaint an engine unless it has been repainted before. Much is destroyed when repainting, even if there is little or no paint left. Mechanical restorations are done as needed.
Wayne Grenning, of Lockport, N.Y., takes this idea one step further. He will actually un-restore an engine.
Here are two photos of a 2-1/2 HP Cook, circa 1903, that he owns. The before photo is the one with the oak cart and the fresh coat of green paint. The after photo shows the results of his "un-restoration." Through a process known only to him, he reproduced the patina of an engine that has been neglected for many years. There is a large frost crack in the side of the cylinder that has been brazed shut, but you would have to know it was there in order to see it after the treatment he gave the engine. Woody Sins, 3 Edna Terrace, New Hartford, NY 13413; email@example.com