MG TC lore says that tappet clearances "are set to .019 in. Inlet and Exhaust, when the engine is hot". and goes on to say that this is effected "by rotating the adjustment screw with a screwdriver and checking with a feeler gauge of the correct thickness".

I have a better way.

Firstly, do it with a cold engine, its easier, trust me. Perhaps back in the 50's the poms, huddled over their TC's in unheated wintry garages needed the heat from a hot engine to prevent their hands freezing to the engine.

Secondly, throw away your feeler gauge and try this:- The TC tappet adjusting screw thread pitch is 25 turns per inch, i.e one turn = .040 in or 40 'thou', half a turn therefore = 20 'thou'. To set the tappet clearance turn the tappet screw by hand to take up all the slack between tappet and valve, unscrew precisely half a turn and lock in this position with the lock screw. This sets the tappet clearance precisely to 20 'thou' cold which translates to around 19 'thou' hot.

Those of you with a fetish for adjusting tappets will know the difficulty in setting accurately with a feeler gauge. After 50 years or so the tappet rocker on your TC develops an indentation where it impinges on the valve stem, this makes it difficult/impossible to insert your feeler gauge and measure accurately the clearance between rocker and valve. You could remove the rockers and with a file remove the indentation but that's not a very bright thing to do as the case hardened rockers would be weakened, you could buy new rockers (US$34:95 each (Moss Motors April 98 Catalogue) x 8 = $279:60 - good luck) or you could try my simpler, easier, most accurate method.

David Eckersley.