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I'm gonna install 2 electric fans in a my 74 SBC, with 2 temp sensors.
One of them will be located on the manifold intake but I'm not pretty sure about the second one.
There is one plug on top of the water pump where it may be installed on, but I'm not sure whether being a good location or not, besides I will need a reducer to install the sensor. (I think the thread is 3/4")
Any recommendation about a location for the second one?
This is the sensor, with the adapter it came with (no suitable for the thread on the water plug)
I would do the original stock location in the driver side cylinder head between #1 and #3 cylinders.
I'm already using that one, sending unit, for the temperature gauge
Originally Posted by TimAT
How about the right head between 6 and 8?
I was seeking to avoid that location because I thought that Hedman headers might transfer too much hot to the wiring and the sensor per se...but it's true that that there is a solution for that...actually the sensor located between cylinders #1 and 3 is in a similar place.
I'm sure i'll be preaching to the choir, but just in case. Please remember to NOT put teflon tape on the sending unit (Pipe threads don't need it and it interferes with resistance reading). I fought ghost temps for quite a while until i replaced the sending unit with NO teflon tape. Now i get perfect temp readings and it's on the drivers head between cylinder 1 and 3.
I'm sure i'll be preaching to the choir, but just in case. Please remember to NOT put teflon tape on the sending unit (Pipe threads don't need it and it interferes with resistance reading). I fought ghost temps for quite a while until i replaced the sending unit with NO teflon tape. Now i get perfect temp readings and it's on the drivers head between cylinder 1 and 3.
I read that on other post. I use to see that they have some kind of loctite sea or locker. Then, nothing need to be put on them?...Hard to believe they won't leak
Last edited by corvetero; Jul 3, 2017 at 12:38 AM.
I read that on other post. I use to see that they have some kind of loctite sea or locker. Then, nothing need to be put on them?...Hard to believe they won't leak
I'm with you. I used both liquid and tape teflon on mine. But this last time was bare brass and zero leaks and most importantly a stable cooling system!
Use a regular pipe thread sealant. There will still be points of direct contact between the threads which will conduct electricity. That may not be the case with a [solid] Teflon tape.
If you use the port in the water pump, just be aware that is water coming from the radiator, so cooler than the water in the intake manifold going to the radiator.
I used this on my truck and 71. Just be aware that when you shut the engine off the heat will rise into the neck and turn on the fan. I used a switched feed for the relay to shut off the fan when the ignition is off.
The fan will also start when you go to start up a hot engine unless you use a switched power source, one that is also off when cranking.
Use a regular pipe thread sealant. There will still be points of direct contact between the threads which will conduct electricity. That may not be the case with a [solid] Teflon tape.
I already use teflon tape and check continuity between the sensor housing and the intake, it grounds perfectly, but your it seems to be a better option.
Originally Posted by '75
If you use the port in the water pump, just be aware that is water coming from the radiator, so cooler than the water in the intake manifold going to the radiator.
Good point, I am also thinking that if for some reason I put the sensor on the thermostat housing and thermostat get closed stuck, the fan would not start since the sensor is not getting the real temperature hence not grounding.
In a C3, water comes FROM the radiator and TO the water pump via the lower "suction" hose. From the pump it goes into the engine, through the heads, and out the intake manifold outlet via the thermostat. That outlet port is exactly where you want to measure the water temp, as it has just left the cylinder heads and SHOULD be at the maximum coolant temp point.
In a C3, water comes FROM the radiator and TO the water pump via the lower "suction" hose. From the pump it goes into the engine, through the heads, and out the intake manifold outlet via the thermostat. That outlet port is exactly where you want to measure the water temp, as it has just left the cylinder heads and SHOULD be at the maximum coolant temp point.
Do you know what's the reducer type I need to plug the sensor on top of the water pump. Might be 3/4" NPT to 5/8 ?
In a C3, water comes FROM the radiator and TO the water pump via the lower "suction" hose. From the pump it goes into the engine, through the heads, and out the intake manifold outlet via the thermostat. That outlet port is exactly where you want to measure the water temp, as it has just left the cylinder heads and SHOULD be at the maximum coolant temp point.
Well aware of this, that's why the water at the pump is slightly cooler as it has just come from the radiator.
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Temperature sensors
