Could have found this much earlier but I wanted to give the engine and all ancillaries a good check. As Cylinder number 1 is slightly down on compression next on the list was the valve gear. But removing the cam cover didn't reveal any horrors. No broken rockers or shattered cam followers. And the valve clearances, though not spot on, didn't need immediate adjustment. Even the (adjustable) cam sprocket hadn't slipped and still was in its correct position. So no major thing wrong in that area. Rather glad about that, although I'll probably adjust the valve clearances this winter when the car needs to be stored for three months. This is due to a new and rather stupid politically inspired legislation regarding cars aged between 25 and 40 years.
And while over at a friend's work shop last week he pointed me to a probable mistake I might have made regarding the ballast wire. It turned out he was correct. I had taken a wrong measurement, with the dizzy timing in the wrong position. As a result I wasn't measuring the current over the ballast wire but the battery's voltage. Another of his tips was to start the engine with the fuel supply shit off to clean out as much fuel from the engine as possible. So after starting the engine with the fuel pump switched off, I did another check of the ballast wire. With the ignition switched on and the dizzy's chopper disc in the correct position I got a reading of approximately 6 Volts. Result, both ballast wire and my rewiring for the switch panel OK. And to rule out any other ignition problems I compared the fitted coil with a new one. With readings of 1,8 Ω for the primary winding and 13,1 KΩ for the secondary winding this turned out to be fairly close to the fitted coil. Again no problem there.
After that I removed the spark plugs, so any remaining fuel could evaporate over night. Biggest advantage of starting the engine for a short time, is that it soils the spark plugs a little. As a result of this, the clean washed number three spark plug, now clearly showed what was wrong, a cracked insulator tip.
And this matches nicely with the symptoms of the engine. At this point I did start the engine and it was a big improvement, though not brilliant. But as the last item to check was still on the "list" I decided to wait for that to be finished before going for a test drive. So this morning I started replacing the fuel filter fitted between the tank and the fuel pump. I had high hopes this job could be finished before noon, but a few things decided to put up a fight. In the end I managed to renew the filter and clean up the pump. For good measure I opened the pump to see if there was any dirt in its filter, but it was immaculate inside.
So with everything back in place it was time for a little test drive. The engine started promptly but settled at a slightly lumpy idle. Driving of clearly showed an improvement, but once the engine had warmed up it started to misfire under load at lower revs. Ones the revs rose it behaved reasonably well, though still lacking some grunt and struggling slightly. At least she idles fairly normal once on temperature, so clearly there is progress. The search continues!