Oil Pressure and Coolant Temp Sending Units

[ChrisCostlow]

Hi Everyone

I have a new crate 350HO in my '72 Blazer. When it's running, the oil pressure gauge is pegged and the temp gauge never moves. I'm assuming it's because the gauges in the dash need a different electrical signal than what they're getting from the sending units with the newer engine.

Can I buy 72 era sending units and swap them with what's currently installed? It's still a Chevy Small Block, right?

Thanks in Advance!

Chris

[TBONE1964]

Originally Posted by ChrisCostlow

Hi Everyone

I have a new crate 350HO in my '72 Blazer. When it's running, the oil pressure gauge is pegged and the temp gauge never moves. I'm assuming it's because the gauges in the dash need a different electrical signal than what they're getting from the sending units with the newer engine.

Can I buy 72 era sending units and swap them with what's currently installed? It's still a Chevy Small Block, right?

Thanks in Advance!

Chris

Hi Chris,

Order your temp sending unit for a 72 K5 with a 350. This will make sure the sending unit matches the gauge. Not sure what your new engine has but I would change just for piece of mind.

To test your temp gauge, pull the green wire from the sending unit and ground it with the ign key in the run position. If the gauge pegs, you should be OK with gauge and wiring. Have some one watch the gauge as you ground the wire. You only want to touch it to ground briefly. If the gauge does not move, then check for power at the number 3 terminal on the cluster connector. This is hot feed for temp and fuel gauge. It is a pink wire.

For the oil pressure, you should be mechanical with an oil line from engine to gauge. It is not uncommon to reach over 80 psi of oil pressure in a fresh engine when it is cold.

I do offer good used 80 psi oil gauges if you are in need. You can also test with an aftermarket gauge such as a 100 psi Autometer style. At least this will give you some piece of mind that the gauge is working correctly.

Hope this helps, let me know
Tom

[kazoocruiser]

Originally Posted by ChrisCostlow

Hi Everyone

I have a new crate 350HO in my '72 Blazer. When it's running, the oil pressure gauge is pegged and the temp gauge never moves. I'm assuming it's because the gauges in the dash need a different electrical signal than what they're getting from the sending units with the newer engine.

Can I buy 72 era sending units and swap them with what's currently installed? It's still a Chevy Small Block, right?

Thanks in Advance!

Chris

It is likely that the coolant switch you are plugged into now is a temperature switch, and not a temperature sensor. It stays open at normal temperatures, and provides the ground when the engine overheats to turn on the light in the dash. That is the light that tells you when to buy a new motor. You will need a sensor that can provide a floating ground. The sensor operates like the sensor in the fuel tank.

The other switch you are hooked into sounds like another off-on device. It controls when the oil light in the dash goes on. In that case, you might want to keep it, and extend off the block with a tee and install your pressure sensor there.

[Leigh222]

If the 350HO you have installed has vortec heads you will need to find the correct temp sensor i believe the temp sensor threads on vortec heads are 3/8" as opposed to 1/2" for non vortec heads. Most 3/8" temp senders are not the correct resistance rating for our old trucks. You can either have a 1/2" unit machined down or purchase a correct ohm 3/8" sender. I'll look to see what I used.

[Leigh222]

Temperature sensor that I used for my 350 with vortec heads is ACDelco 213-80. The sensor can be found on Amazon although it is quite pricey it does the job.

[ChrisCostlow]

I'll be looking into that sensor this weekend.