This is a photo of #4 Piston on a O-360 A4K newly remanufactured by Lycoming with test cell time only. (roller cam and all) This engine has not flown yet, when it arrived in the crate we pulled all 4 cylinders and sent them to Lycon (Visalia Ca.) for their porting and flow matching. The next photo is #1 piston which exhibits considerably less carbon deposits then #4. The amount of deposits between the cylinders is random which is the reason for the flow matching. Trivia: which way would the swirls go at the equator?