Morris Minor Owners Club

Just to let you all know, I'm running with one of those in-tank fuel catalyst devices and the car runs perfectly.

I know they're probably a load of rubbish (basically a small sack of tin) but after fitting mine last august I've no had any timing related problems and did initlally notice an improvement in performance.
My 'logic' is, I'm going to buy an unleaded head sometime anyway so who cares if my valves do get brunt to a crisp.

Anyone else tried them?

(note, I don't work for any of these people and won't start spouting BS about how the russian army/top scientists/god himself/etc.. have endorsed them!)

They simply don't work and the companies won't submit any samples for testing. They won't damage anything as they just don't do anything!

Exactly - I have run for 6 years (and a hard driven 10,000 miles) without any additives or in-line catalyst - and no trouble so far. You are correct - the only harm will be to the valve seats, and that's the bit you will then replace when the time comes - or just fit another head. Keep an eye on the valve gaps - if they start to close up then there may be trouble ahead.