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Hold the phone. I'm probably not going to be able to drive my beetle to Oshkosh this year. I think some part of the engine is nearing the end of a wear cycle.
I was all jazzed thinking that since it's still April, I have enough time to get the paint patched a little, and wax it, and get the brakes recondition and the engine running right so that I can take it cross country. Recently, I got enough equipment to actually check the timing of the engine so that I can get that right. That's all part of the plan to get the engine idling right.
Now that I can measure and set all the parameters, I am planning to go through the full tune-up procedure. First, that starts with setting the valves, a very important operation in an engine with solid (non-hydraulic) valve lifters. The only other time I set the valves in this car was about 1000 miles ago. At that time, both of cylinder #1's valves were way too tight (the #1 exhaust valve clearance was too small to measure), but the others weren't too far off. I set all the valves to .006 inches clearance.
Well, this last Saturday, I went to set them again, and the #1 exhaust valve was once again too narrow a gap to measure (#2 had drifted slightly, #3 and #4 all valves were still dead on). Uh oh. The #1 exhaust measurement is bad news. The valve has moved catastrophically out of adjustment in 1000 miles of driving, for an adjustment that's normally done every 6000 miles. That means that something is severely changing shape or length in the engine, which isn't a good thing. According to the lore, it means that the #1 exhaust valve is burning; that is, it's letting exhaust gases go by it and the gasses are acting like a cutting torch, making the valve stretch (causing the change in valve train geometry) and will eventually will break the head off the valve and cause catastrophic engine damage.
The first time I set the valve clearances, I noticed the heads weren't the same. This time I took photos:
Right hand side; this is the one that's failing
Left hand side; this one is doing fine
Left hand side close-up of the casting number
The two heads are the same part number (113 111 375A) but different casting numbers, 66 for the left and 157 for the right. I'm not sure what I can conclude about the casting numbers. Perhaps the only thing is that I can be mostly sure that those heads aren't both originally. Perhaps the right head, the one that's failing, is orginal and now it's finally failing. The left one started to fail a long time ago, and so it was replaced, which is why it's still working fine. So...looks like I'm going to need to go shopping for cylinder heads.