Applying the Correct Torque
When installing a new spark plug, ALWAYS follow the instructions listed in the manufacturer's literature. Improper torqueing can lead to engine damage. The information provided below has been estimated for standard engines.:
- The first step required for proper torqueing of a new replacement plug is to ensure you have clean thread surfaces. Clean threads will allow for a proper seal and maximum performance.
- If anti-seize compound is to be used, it should be applied sparingly because this could foul the plug and produce excessive carbon build-up on the threads, as well as give off fumes once the engine reaches operating temperature.
- Torque requirements vary greatly from engine to engine. Care must be taken when torqueing spark plugs, especially in softer aluminum cylinder heads. When in doubt, always check your manufacturer's literature.
- The proper torque of a spark plug can only be achieved using a torque wrench. In the absence of this tool, the table below provides a generic guide to torqueing a replacement plug based on the number of turns after the plug becomes finger-tight.
- The table below lists the torqueing specifications for most spark plugs being installed in either cast iron or aluminum cylinder heads.
- Torque values assume clean, dry threads. The use of anti-seize or thread lubricants will modify these values unpredictably, so read the product instructions carefully before proceeding.
Installation Without a Torque Wrench:
In most engines, replacement plugs can be installed without using a torque wrench but extra care should be taken to ensure the new spark plug seats and seals properly. If you are inspecting and replacing an existing plug, be sure to use a wire brush to clean any debris from the plug's threads.
A tapered-seat spark plug should be tightened by 1/16th of a turn past finger tight. See the illustration above. NOTE: If you have high performance alloy or aluminum heads, always use a torque wrench to eliminate any possibility of damaging the engine's internal threads.