What should spark plugs be torqued to

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. 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.

Toggle navigation. Torque Installation Chart When installing a new spark plug, always follow the instructions listed in the engine manufacturer's literature. The information provided below has been estimated for standard engines: The first step required for proper torquing of a new replacement plug is to ensure you have clean thread surfaces. Clean threads will allow for a proper seal and maximum performance. A spark plug that is under-torqued will not be fully seated in the cylinder head and heat dissipation will be slowed.

As a result, the firing end of the spark plug can overheat and pre-ignition can occur. Serious engine damage can follow.

Over torque can cause the metal shell of the plug to stretch. Stretching of the spark plug metal shell can break the inner gas seals or cause a fracture in the spark plug insulator. For proper spark plug installation, it is always highly recommended to use spark plug removal and installation tool and spark plug torque wrench.

Correct torque is the very most critical step of spark plug installation. If the torque is exceeded, the spark plug shell can be stretched, thermal characteristics can be lost and there may even occur a rupture of the spark plug during its assembly or dismantling in the engine It is extremly important not to exceed the installation torque. This will help ensure proper seating and adequate heat transfer. This goes for conical seat spark plugs only!

How to change conical tapered seat spark plug without torque wrench - only if torque wrench can not be obtained. When replacing spark plugs without spark plug torque wrench, spark plugs should be thread-in by spark plug removal and installation tool , or socket by hand wihtout spark plug wrench untill they fully seat. Then a spark plug wrench should be used to tighten the spark plug by turning an additional angle as follow:. Sealing with a gasket washer - spark plugs can never be mounted into cylinder head without a sealing gasket washer.

In this case sealing washer must be used comes with new spark plugs.