[snowtire]

Thanks for the advice. I had on my checklist to pull the other five plugs to check whether they are bunged up in the same way.

I have completely rebuild a VW diesel engine before, and have had the motor out of two VW Vanagons and a '66 912. So in terms of skill, I am not afraid of too much. It's just that given my work and family schedules right now I am not relishing the thought of pulling a motor and spending the next few months getting dirty every night after the kids are in bed, ordering parts, and feverishly looking at this forum every five minutes. I do have a mechanic who would possibly let me drop the motor at his place.

I think for now I will try the least invasive first step, which is to chase the threads very carefully and look for other plugs with the same problem. If I find others with the same problem, I will have to reassess. I was hoping to drain the oil on Friday night (HOT) and adjust the valves on Saturday morning. This spark plug deal takes precedence, though, not least because I can't get the oil hot with only five spark plugs...