'Rule of Nine'

'Rule of Nine' valve clearance adjustment:

With the plugs out turn the engine until any tappet goes fully down. Count the valves from the front of the engine to that valve, take that number from nine, then count to that number from the front of the engine again and adjust that valve. Then turn the engine until another valve goes down and so on.

Or even easier, after counting from one end to the valve that is down, count the same number from the other end and adjust that one.

You don't need to adjust them in any particular order, just according to which one goes down next, that way you will have adjusted them all in two complete rotations of the engine.

You can turn the engine either with a socket on the crank pulley (1 5/16" AF, same as for the Salisbury/Tube-type rear axle hub nut), which tends to slip off and space is limited on all but 1977 and later model cars, or put the gearbox into 4th and nudge the car along forwards to turn the engine. If you run out of space knock it out of gear, roll the car back, put it back in gear, then nudge forwards again and so on.

However this does pre-suppose that the greatest gap occurs at the strict rule of nine point, but several valves on mine don't, neither does a pals and others have said the same thing. In theory, and John Twist has said this, anywhere on the back of the cam from where the lobe is should be OK as it should be a circle. But mine obviously aren't, and I have to nudge the engine several degrees one side or the other of the strict rule of nine point on the back few valves to find the point of greatest gap. Without that, every time I try and measure the gaps they are either bigger or smaller than they should be.