Spark Plug Installation Instructions:
1. Bosch Double Ir spark plugs come gapped from the factory at 0.012”. If this suits your application, there is no need to gap the plugs. To open the gap, gently pull the ground electrode back with a spark plug gapping tool. Do not force a feeler gauge between the electrodes and pry them apart. This could damage the precious metal pads and cause premature failure. If you want to close the gap, gently tap the spark plug on a solid surface to bend the ground electrode.
2. For Landfill applications, anti-seize is highly recommended. Bosch recommends Loctite Heavy Duty Metal Free anti-seize part number 51605. When applying anti-seize, only put a small amount at the base of the spark plug. Too much anti-seize can have the opposite effect and cause the plugs to stick in the cylinder.
3. With the spark plugs ready to be installed, lock the engine down for safety. Remove the ignition cables and coils. Remove the worn spark plugs and ensure no dirt or oil enters the combustion chamber. Also make sure the crush washer is still on the removed plug.
4. Clean the threads of the cylinder head using a thread chaser. This helps prevent plug seizure.
5. The engine is now ready for the new plugs. Use a socket that holds the plugs in place to prevent them from falling during installation. Always use a socket that has a wide bore that does not contact the ceramic. A socket with supports or that is not fully seated on the hex will cause cracks in the ceramic and may even break the plug.
6. Always use a torque wrench to install the plugs.
For 18mm plugs, such as the 7305 and 7306, use the below specifications:
With Anti-seize: Torque to 26lb-ft
Without Anti-seize: Torque to 33lb-ft
7. With all the plugs installed, reconnect the ignition coils and cables. Unlock the engine and installation is complete.