How to Set Tappets Using the 'Rule of Nine'

There is a general rule which applies to setting valves though, and it's called the rule of nine. And even that route, you can set valves using the rule of nine, but I would stress that one or two engines this doesn't work with, so do check your handbook. Now the way the rule of nine works is this. We actually watch the valve that's being held fully open. So at the moment, I'll just turn this engine back a little bit, and then turn it in its direction of travel. Watch valve number eight here. This is a front of the engine, so this is valve number one. Here's the back of the engine, valve number eight. Watch valve number eight, watch that go down there. Now that's as far down as it will go. Valve number eight is right the way open. So what the rule of nine says is, we take eight away from nine, leaves us with one, we adjust valve number one.