I swapped an LS1 into my '69 and wanted to use the factory gauges.
I tried to find a modern 12mm sending unit that had the correct resistance range to put the gauge needle in the center of it's travel at operating temperature.
I have not been able to find one.
The 12mm ones that fit the LS heads don't make the needle rise far enough.
The 1/2" threaded one that is supposed to be on the original small block makes the needle read too high.
I found a 12mm to 1/2" adapter but that sticks very far out of the head, looks awful and probably doesn't give an accurate reading.
I wound up drilling and tapping a 1/2" pipe thread into a flat blank spot on my water pump and installed the stock sending unit there.
The trick to making this work is to add a 10 ohm 1/4 watt in line resistor to the wire that goes to the sending unit.
I tried a bunch of different resistor values before settling on this one.
Now when the LS is at 200 degrees the needle is right in the center of it's range!
I checked the temperature with the Torque App to compare with the gauge reading as I tried the different resistors.
You can see in the first picture that I used a piece of WD-40 can straw inside the heat shrink to give a little support to the resistor to keep it from bendig too much.
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I tried to find a modern 12mm sending unit that had the correct resistance range to put the gauge needle in the center of it's travel at operating temperature.
I have not been able to find one.
The 12mm ones that fit the LS heads don't make the needle rise far enough.
The 1/2" threaded one that is supposed to be on the original small block makes the needle read too high.
I found a 12mm to 1/2" adapter but that sticks very far out of the head, looks awful and probably doesn't give an accurate reading.
I wound up drilling and tapping a 1/2" pipe thread into a flat blank spot on my water pump and installed the stock sending unit there.
The trick to making this work is to add a 10 ohm 1/4 watt in line resistor to the wire that goes to the sending unit.
I tried a bunch of different resistor values before settling on this one.
Now when the LS is at 200 degrees the needle is right in the center of it's range!
I checked the temperature with the Torque App to compare with the gauge reading as I tried the different resistors.
You can see in the first picture that I used a piece of WD-40 can straw inside the heat shrink to give a little support to the resistor to keep it from bendig too much.
