Yes, after Gretna I completely stripped the cams down and put the originals back in. Turned out that the offset dowel on the inlet cam had rotated, so was retarding it rather than advancing - leading to too much cam overlap. How that happened I have no idea, but the dowel is now completely wedged in the cam and will need drilling out.
Anyway, that plus the o2 sensor has it running properly when it's warm, can see the sensor working on the live data now too.
The head was a new one that went to DVA power for building up. Other than some of the valve guides being slightly oversize there was nothing noted (and even then, Dave's words were "not suitable for a race engine but more than OK for normal use").
We're not talking a few seconds of rough running here, like you get with a coolant leak, but several minutes - before lockdown, my normal routine was to start the car, go in and have breakfast, and then it would just about be running smoothly by the time I'd eaten (around 10mins probably).
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