2. Use a generous amount of heavy grease on the drill bit and tap to capture any metal shavings or contaminates left as a result of the drilling and tapping process. Always use a small magnet after the process to ensure that you have retrieved any metal shavings prior to installation of the thermocouple.
3. Drill a 5/16” hole in the manifold. Using a 1/8” National Pipe Tap (NPT), which can be purchased at any hardware store, tap the hole. Be sure to follow the instructions included with the tap. The tap will be tapered and you want to tap the hole only until the threads of the tap are slightly deeper than the inside of the manifold. Be careful not to tap too deeply into the manifold as the fitting on the thermocouple will have to be screwed in deeply.
4. Once the drilling and tapping are complete, check to make sure there are no metal shavings in the manifold. If you see shavings or contaminates, remove them before inserting the thermocouple. Install the fitting by screwing the tapered end of the fitting into the manifold. The tip of the fitting should be flush with the inside of the exhaust path, but not any deeper. Tighten the fitting with a small wrench or socket, but be sure not to over-torque the fitting. Insert the probe into the fitting so that the tip is in the center of the exhaust flow path. Tighten the top nut on the fitting just tight enough to keep the thermocouple firmly in position.