I've got DeWitts alum radiator and dual SPALs for my '71 small block. I also purchased the PWM controller for the fans.

I'm looking for a coolant sensor to screw into the passenger-side of the block. A couple of guys here have used a NAPA part ECHTS 3001 / alternate part# TW43 that fits the electrical connection perfectly but on my car doesn't fit the side of the cylinder head (part is too small).

My cylinder head wants a larger 3/4" coarse thread fitting, but the part I bought is 3/8" and fine thread.

Does anyone know of a part number that will work, or is there a mating sleeve that will adapt the new part to my "old" cylinder head?

Thanks for the help...

 

If nobody else replies, then go down the local hardware store and see what they have. I had the opposite problem when trying to install my stock electric fan sensor in new Dart heads.

 

Why not call Dewitts? This sounds like a pretty standard problem that they'd be able to answer.

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I have a Spal fan for my ZZ4. The Spal fan temp sensor, which looks like a 3/8, screws into the appropriate hole in the aluminum heads of the ZZ4. My traditional 68 temperature gauge sensor looks like a 3/4". (I could go out and measure these things, but for now I think this is enough accuracy for conversation.) Not to worry, my Edelbrock aluminum water pump has a 3/4 inch thread opening in the top (for a bypass?), and I've installed my stock 68 temperature guage sensor in this hole. Opps! now the stock wiring harness for a 68 will not mate up to the stock sensor in the water pump. (The stock harness will fit the 68 water temperature sensor in the cylinder head.) Solution: Lectric Limited sells a piece of wiring with the correct connector and correct shielding as an add on piece. I'll use this to give my non-stock location of the 3/4"temp sensor. a "stock" like appearance with the correct factory looking shielded wire.
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It's really great Edelbrock has this 3/4" (?) opening in the top of their water pump. What this means, is that when you add coolant, you can open this fitting and eliminate an air bubble in the top of the water pump impeller chamber. (My Edelbrock pump is a reverse rotation aluminum water pump to accomodate my Serpentine GM Performance system.)

 

Search your friendly local hardware for a 3/4"NPT to 3/8"NPT reducer bushing......

 

I have a Borg Warner P/N: WT3000 I picked it up from Pep Boys. It fits in the manifold perfect. Much debate has been raised about what is the best location. My thought is that with this temp controller you can set the on off to what you want so an exact temp is not as important. I would prefer to have my to have the best location. Hope this helps.
Waterplay

 

or you can use the stock guage sender. A lot of people don't realize the SPAL controller is capable of using the GM sender at the same time using it for the gauge. The only thing you have to change is on single pole senders you have to cut the plug off and use only the green wire. Tap this wire into the stock sending unit, cut off the black wire and wrap it into the harness.