454 long block replacement and associated sensor issues

[91 Jimmy]

You don't need #3 if your vehicle is now carbureted and running a mechanical fuel pump. That oil pressure/fuel pump switch is required with an electric fuel pump in the event of a crash and subsequent loss of oil pressure when the engine dies, it opens the circuit to the fuel pump so it shuts off and doesn't keep pumping fuel up to the engine and start/feed a potential fire. When you turn the key on with the original system, or any modern vehicle for that matter, you hear the fuel pump kick on for a few seconds and shut off, and then when you crank the engine and it fires up and the system/sensor/switch sees oil pressure it closes the circuit so the fuel pump will run while the engine is running. No oil pressure at that location= no electric fuel pump.

OK, that's what I thought. Now for the next question; here is a side by side of the oil pressure sensor (or switch, I'm not sure what the difference is?) I bought from Rockauto vs. the one that was on the old engine:

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The new one is a little longer, but they both have the same thread which brings me to the following question: The thread on the Tee is larger than the thread on either the new or old oil pressure sensor so I can't thread it directly into the block. So, do I use the tee but plug the other end if I don't need number 3 in the schematic above as QBuff02 mentions?

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[AuroraGirl]

OK, that's what I thought. Now for the next question; here is a side by side of the oil pressure sensor (or switch, I'm not sure what the difference is?) I bought from Rockauto vs. the one that was on the old engine:

You must be registered for see images attach

The new one is a little longer, but they both have the same thread which brings me to the following question: The thread on the Tee is larger than the thread on either the new or old oil pressure sensor so I can't thread it directly into the block. So, do I use the tee but plug the other end if I don't need number 3 in the schematic above as QBuff02 mentions?

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with the one tab on the thing, I would be tempted to tell you the thing relies on the threads to ground properly. You may want to undo some of your PTFE there so the threads can contact metal. If that was an issue you found
Also, because your engine was designed to have both the Sensors on that distribution block, I would say you are correct in that you should clean it up, plug the unused one(carb from efi, right?) and thread back in and go that way. Otherwise, I would think a non EFI sending unit would be the right thread size unless it was made bigger for the t for the 2 sensors. (factory wise\)

 

[Turbo4whl]

OK, that's what I thought. Now for the next question; here is a side by side of the oil pressure sensor (or switch, I'm not sure what the difference is?) I bought from Rockauto vs. the one that was on the old engine:

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The new one is a little longer, but they both have the same thread which brings me to the following question: The thread on the Tee is larger than the thread on either the new or old oil pressure sensor so I can't thread it directly into the block. So, do I use the tee but plug the other end if I don't need number 3 in the schematic above as QBuff02 mentions?

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You could just use a pipe bushing, 1/8 pipe to 1/4 pipe.

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Any local hardware/ home store will have this.