Morris Minor Owners Club

if its carbon stopping the plugs going in all the way causing your air leak (which it sounds like it is ) i have a thread chaser you could borrow if you are close to me

Just cut a slot in the thread of an old plug - squirt WD40 on the thread - and carefully use that as a thread cleaner... You are using plugs with a sealing washer - and not plugs with a 'taper seat' ?? However I have to say I rather doubt this is the reason for the 'black' plugs - but may well be why #2 is a bit 'down' on the test.

Thanks for the offer big Jim but I'm near lewes in east Sussex so miles away! Ill clean out the threads on the head, and check to make sure sealing surfaces are ok

Same as bmc above but it is easier to file a small flat on an old plug and use that as a plug chaser. Grease the threads of the plug chaser before use and the majority of the crud will stick to the plug chaser rather than fall into the cylinder. With all the plugs out give the engine a quick spin over to blow any crud out of the bores.
Job done simples

Well we now have a great idle and great top end but...... He misses a beat when accelerating and I have 2 black plugs (still 2&3) and 2 white plugs! 1&2

Huh?

I have 2 black plugs (still 2&3) and 2 white plugs! 1&2

So #2 is both black and white?

Someone else had similar just recently....and it was caused by manifold distortion. The only 'common' point to 2 and 3 is the central exhaust manifold connection - I can't directly see how that could cause 'black' plugs, although it's possible if the exhaust connections at 1 and 4 are not tightly sealed to the head - they may somehow be allowing air to flow back in, causing the 1 and 4 plugs to be white. It's all I can see that is common - so would be worth checking it out.

Surely though if the valves are seating Ok no air would get through? Noticed today the missing is unbearable when the engine has warmed up after 30 mins.....

There is a 'pulsing/reflecting' flow in the ports - air could be sucked back in...... Sorry - I can't see ANY other commonality between 2 & 3, and 1 and 4........ Initially - just tighten the manifold nuts to see if that helps........