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. And type of gauges. Meaning if you've got an oil pressure light you need an oil pressure switch for the light. If you have a gauge you need a sender that matches the gauge. Etc.etc.

 

[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.

 

[Dejure]

YEARS ago, I moved all my gauges into an overhead display. I ran the wires up the window post (had to drill two holes) and go from pressure line to electronic. I don't remember all the details on how I picked gauges out, but I remember I didn't have to swap senders on other than the oil pressure.

Thinking on it, rather than it being about a given year, it MIGHT be more accurate to say it's about determining the sending unit's details.

For example, when looking for a fuel gauge, for the new dash I'm going to build for my 78 [like I did on my old 69 C10), I have to buy a gauge for 0 to 90 ohms with 0 being empty.

 

[Goldilocks77]

I’ve personally had problems matching up the right sensor for the stock temp gauge in my 77 C20. The first one I picked up had me freaked out after a top end rebuild of my GM crate 350, telling me that I was overheating. After no evidence of such a thing I swapped it out to a different sensor that now tells me that the engine never actually warms up. In light of the OP question, is there a resource to find out what is the correct sensor for the specific application? In my case, good luck telling the folks down at O’ Reilly that you’ve got a 77 Chevy C20 with a crate 350 model number 19210009 and you need an engine part.

 

[Dejure]

Goldiolocks, I have a feeling it's all about rabbit trails.

On the upside, the Net gives us rabbit trails that, eventually, can get us where we need to be [on the matter of relative information].

ONE of the search means I've found worth its bits and bites weight is, PERPLEXITY.

I qualify that with that I, often, have to reform my inquiries and it, frequently, occurs I get led down a path I need to go down to get where I need to be. THAT is how I learned Chevs and their GMC versions use a 0-90 ohm sender unit for the gas gauge.

 

[projo198]

This may not be of great use to you, but I had the same issue a few years back finding the correct temp sensor for my '82 with a 305 motor. I eventually tried the following at it worked, so when shopping for your 350 and you see this pick the OTHER option lol.

I can't help you with the oil pressure sensor, but worst case you could run a manual gauge and line instead. The whole setup is very cheap at local part stores (minus the gauge of course).

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