I have a 62 Buick Invicta wagon with a 401/sp400 from a 66 wildcat. Anything that can be bolted to the engine from the outside has been replaced or rebuilt. I have dual glasspacks. It has a pretty noticeable miss on idle and backfired occasionally, and it will occasionally suck a dollar bill up to the pipe when you hold it up to it. I’m guessing it’s valve/lifter related. I haven’t torn into the engine any. I’ve probably put 3000 miles or more on it in the last 2 years. Curious as to what remedies I can try before I start pulling the valve covers. I’ve heard sea foam and marvels recommended in passing but I’ve also heard not to use any solvents. Thanks in advance Sent from my iPhone using H.A.M.B.