Instrument cluster questions on new build

[nicofan96]

I have a 1979 GMC sierra C-15. It came originally with a straight 6 engine but has been replaced with a 350. Since the engine has been replaced the oil pressure and engine temp gauges do not work. I have heard that the gauges can be replaced with the 350 gauges or the sensors can be replaced with the straight 6 sensors to correct. Any inputs on what direction to go?

 

[75gmck25]

Oil pressure sensor should be the same for all the engines. Pressure is pressure. Temp sensor might be different, but I think they are the same resistance for each year, regardless of engine. However, SBC 350 usually has a 1/2” thread, and some older SBC’s used 3/8”; not sure about 6 cylinder.

 

[Ricko1966]

^^^^^^ senders have to match the year of the gauge cluster.

 

[nicofan96]

The oil pressure sensor has electrical connections. Is it not based on resistance?

 

[75gmck25]

Right, the oil pressure gauge reading is also based on sender resistance.

However, I've never seen anyone who struggled to match the oil pressure gauge sender like you have to do for the temp sensor. Based on RockAuto listings, the key features to check for are gauge vs. light sending unit, and does it have the correct threads. I assume the oil pressure senders are more consistent across years and engines.

In this video the guy says that 78-87 squarebodies all used the same oil pressure sending unit. YMMV.

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[nicofan96]

That video was helpful. I will look at the gauges later today. Thank you for providing that.

 

[Matt69olds]

There are different sending units based on gauge readings. Meaning a gauge that reads to 60psi, requires a 60psi sending unit.

I ran into this years ago with a Grand Prix I had. The factory gauge registered to 80, the 455 Olds I swapped in had a 60psi sender. The gauge was NOT accurate.

If you look on the end of the sender, you will probably see it’s stamped 60 or 80.