Best sparkplugs for Series 2A 2,25 L Petrol, CR 7:1

Which sparkplug is the best for a 2,25 L petrol CR 7:1 series 2A engine which I have in my Series 3 88in from 1979 ?

For quite some time it has not been running smooth

After raising the idle a bit I removed the sparkplug wires one by one.

At the forward cylinder, I did not notice any change, as I did with the other cylinders

Following this, I add a tester between the sparkplug and spark wire and could see that spark at the tester was just as good as the three other cylinders.

I have removed all the spark plugs and from the attached picture it looks like the spark plug from the forward cylinder (left on the picture) is a bit wet.

Could there be something else wrong ?

And yes, I managed to say hello to one of the sparkplugs, in spite of using a special spark wire pulling plier and welding gloves.

Thanks

Søren

Check the distributor cap No1 plug does not look like it has been firing to me unless it has been renewed recently , You could swap No1 to a different position and see if fault follows it.

the answer to your specific question is Champion N.8 or equivalent for the correct gradation of a 7:1 compression ratio.
From the photo some spark plugs thread looks a little wet, is it oil?

Thanks.
I have replaced all the plugs and it sounds like it is running much better now

Up to the time when I ceased servicing my own vehicles several years ago I never used anything but Champion plugs, both in LR products & conventional cars.
If my RRC needs plugs I continue to specify Champs. in my instructions to the garage ... though our non-LR daily driver gets whatever the manuf. states.