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I dont know if everyone reads the blogs so I wanted to ask this question. I finished a few things on the car this weekend and decided to take it for a ride. It started missing under a load and when I got home I noticed 1 of the valves was tapping again. Its the 4th valve from the back of the engine. I know that is 1 of the valve lifters I replaced before. I guess I have to remove the head and replace that lifter again. Does anyone have any other Ideas?

Good Morning…I run Marvel Mystery Oil in both old machines. It does seem to stop sticking valves. I also notice that if I drive both them each week, they run much better than when I don't. Ernie in Arizona

If it's dirt, then maybe one of the additives can dissolve or otherwise clear up the issue after running it a bit. If it is simply marginal, say at hot idle (doesn't sound like your problem) then perhaps Marvel or merely a heavier oil would help. Most likely have to take the head off and replace it.