Coolant Temperature Sensor
Adding fuel injection requires the addition of a coolant temperature sensor. The installation can be done is a couple of different ways as shown below.
The TR6 thermostat housing hose nipple has a straight thread rather than the more common US tapered pipe threads used in today’s cars. Fortunately the original thread, 5/8-18, is slightly smaller than a US 3/8″ pipe thread, making the conversion pretty easy. Just below the thermostat, the hose nipple on the passenger side was removed. The socket was tapped to US 3/8″ NPT (pipe thread) and a 3/8″ NPT brass street tee (NAPA WH 3750×6) threaded in. Be very careful if tapping this yourself to keep the tap straight and check the depth often. Cast iron is tapped dry without lubricant and requires that the tap be backed up often to keep the new threads clear. Because the new threads are tapered, the fittings will only screw in part way. The deeper you tap the further the fittings will screw in. DO NOT FORCE a fitting by overtightening into the cast housing as it will act like a wedge and split your housing. The street tee is male on one end, female in the center and female on the other end. A ½” hose barb with 3/8″ threads (NAPA BK 660-1503) was screwed into one end and the sensor screwed into the center of the tee. A GM style coolant temp sensor (NAPA ECH TS4015) or a 3/8” NPT plug is threaded into the tee and the small coolant hose reconnected. This is another task that can be done prior to the TBI conversion
In this instance the customer decided to mount the sensor upside down directly in the hose. All that was needed was a a 3/8″ NPT Tee and two 3/8″x1/2″ barbs.