Coolant temperature sensor location

Some water pumps (like my Stewart Stage 1) have three ports. I use two for the heater, and one for water pump suction to my expansion tank.

If you are not running this type of setup, you should be able to repurpose the suction connection to a sensor.

I know there are a lot of "ifs" in my suggestion (right waterpump, cooling system connection)...

There are two ports in the water pump that I thinks go the pump impeller suction side cavity. One has the heater return hose. The other is plugged. Since the pump is flowing coolant thru the block regardless of the thermostat position, I think I should get a good representative coolant temp using the plugged location on the water pump.
Agree???

Been doing more reading. The plug I see seems to go into the bypass cavity on the water pump so should see engine block coolant temp under all conditions. This plug may have been used for a thermostatic vacuum switching valve for the emission controls mess they had in the 70s. Am I correct?

I use one of the threaded ports on my Flowcooler water pump for the stock water temp gauge sensor, the other port on the pump is used for the heater hose. I put the EFI water sensor in the block next to the thermostat, I wanted the EFI to read "true" temps from the sensor in the stock location.
The stock gauge seems to "act" the same way with the sensor in its new location.

Bdud, that plugged waterpump port might work for your sensor if there's room; that port gets very close to the alternator body on a 351-C in a Pantera, which is why it's always plugged. Adapting a larger alt etc may force using a longer vee belt but there's a limit to this.

Also, be careful tightening pipe fittings into aluminum water pumps; too much force on the wrench can (and has) cracked pump ports, and it's tricky TIG-welding them without wrecking the pump seal. Several layers of teflon pipe-tape is better than a bigger wrench!

I think it is tight in that area but it does fit. Here is an old picture with a plug in the port. The alternator burst into a ball of smoke so I am now using a ~100amp unit now. I don't use teflon tape on sensors or fittings, there are better sealers out there for that purpose. You also need to be careful with single wire type sensors like the stock units, that need to get an electrical path from the engine to work.

Here is my engine after coming back from the dyno. The 2 wire efi water sensor is screwed into the lower water pump port. The sensors are now swapped around.

Thanks for the help and info. I decided to install it in the water pump port since the alternator bracket/tension arm is directly in front of the block location and there isn't much space. I couldn't install/remove the sensor wire connector without removing the alternator bracket/tension arm. Since the coolant is being sucked from the same cavity in the block into the pump past the second sensor, my guess is that there will be little if any temp difference. You seemed to confirm that noting that the temp gauge reading was the same with the swapped location.
Again - thanks for the help.
Norm