Morris Minor Owners Club

Is it rings or valves?

If I take my plugs out, three are perfect, slightly light brown as they should be but otherwise clean. Cylinder four's plug comes out sooty.

I'm guessing its the valve or seat as its soot rather than oil.
Not too worried as it takes a while to mank up and the car drives perfectly fine, just wanted to confirm suspicions.

If I ever get to the root of my cutting out probs and head over, should be able to get to the root of it with the compression tester (unless you've already got one )

Test as is, then squirt a bit of oil in and test again. If one cylinder is low on the dry test, and they're all pretty close on the wet, then it's rings. If it's still notably low, then it's valves.

If they're all good wet and dry, then it could be guide and/ or seal.