Using the rule of five or seven

Adjusting Tappets

Many common straight four and six cylinder engines follow the rule of five or the rule of seven when it comes to valve gap adjustment.
 
On a four cylinder engine, if you turn the engine over until the valves on cylinder one are rocking, you can check and adjust the valves on cylinder four. Four and one make five. Likewise with the valves on cylinder two rocking, you can adjust the valves on cylinder three and so on.
 
With a six cylinder engine the same rule applies but the numbers should add up to seven, so if the valves on cylinder four are rocking you can check and adjust the valves on cylinder three etc.