Is it guides, or what? It's not seals, 'cause those are new, and it doesn't do what leaking seals would do. Smokes during deceleration on compression only. Nothing at startup, nothing at idle, nothing cruising, nothing at launch. Comp and leakdown show good. The motor is a 351C 4v, and the guides only have about 2k miles on 'em, and are original. They sat unused for some thirty years almost. It's certainly oil burning, and more from the driver's side. Tailpipes get sooty kinda quick. I should say, it seems that oil is being drawn into the combustion chamber when decelerating on compression, if you decel hard for two seconds at high rpm, enough oil gets sucked in to burn off for a couple cycles. I suspect I'm pulling heads soon, just figgered I'd run it by you.