Can someone educate me on online 6 coolant temp sensors

[straight6chevyguy]

Hello everyone, so I'm working on my 76 C10 the truck originally had the integreal manifold head 250 inline six I have swapped in a new rebuilt block and rebuilt Non integreal head.
First off, it has been a few years since I took the original engine out of the truck so my memory is fuzzy on a few things.
Ok so, I'm hooking up my engine bay wires and I noticed that I have two wires that can plug into the temp sensor. Opon inspection I determine that the two wires are connected together. Ok so I know there is a temp sensor that screws into the thermostat housing.
Looking at my old head there is a hole that looks like a temp sensor could go this where my memory is fuzzy as I stripped the old head of all it's usable parts. I'm not finding another temp sensor anything similar In my parts don't know if I misplaced it or what but what I'm getting at is I don't know what was in that hole in the old head or what that second temp sensor wire went to.

I know that the older engines either had one temp sensor either in the thermostat housing or in the head.
So my first question is did 1976 trucks have two temp sensors? Or is it for something else?
And that leads to my main question. If there was originally two sensors will I need two sensors for my idiot light to work correctly?

Also, my new head has the hole for a temp sensor, my original plan was to run the sensor for the idiot light in the thermostat housing and a sensor in the head for an aftermarket mechanical gage, any thoughts on if this would or wouldn't work?

[Short 3/4]

Can’t be of any help with the wiring of that 76, but as far as your last question, I did the same thing on my 65. I really like a good accurate mechanical gauge, but also appreciate that an idiot light immediately grabs your attention. In my case I put the idiot light in the hole in the head, and the gauge feed to the stat housing. Probably could be reversed, but that worked out best in my case.

Also did the same for the oil gauge/light. Was easy, just screwed a small plumbing T into the block, then attached the feeds to it.

Both have been working great now for several years,

Tom

[straight6chevyguy]

Thanks, I agree with you 100% I plan on doing the same with my oil pressure as well.

[Wrenchbender Ret]

Some idiot lights had a cold warning light also. It has a sensor with 2 terminals & 2 wires. The connector had the terms. at a 90 degree angle. It sounds kind of silly but on a cold morning you couldn't wait for that green light to go off. Their was no use turning on the heater till that light went. out.

George

[ray_mcavoy]

Those integral heads often had both a coolant temp sensor and a metal temp sensor. They were wired together (like you found) so either one would turn on the warning light.

[straight6chevyguy]

Thanks guys, it's making sense now.

[chevyguyase]

I have the same coolant sensor hole set up. I can not get a correct reading out of the coolant temp sensor hole in the head. I think because it is to close to the exhaust port. It reads way to hot. I've tried 3 different gauges. I do have my mechanical under dash gauge hooked up to the hole in the head and it constantly reads 250+ degrees. I have to keep my EFI temp sender in the hole in the thermostat housing because I need an accurate input for the ECM. They make a thermostat housing with 2 sensor holes in it, but can't get my hands on one. They also make the part that the thermostat housing bolts to with a sensor hole in it, I can't find one of those either.

[vince1]

I transferred the hot cold idiot light sensor from the 250 over to the 350 when I put it in, so the lights work like they always did. I also added a gauge whose sensor I put in the thermostat housing of the 79 donor engine which was factory threaded. I suspect when that over-temp light comes on the engine would already be way too hot and I feel a lot better being able to monitor the actual temperature.

[Short 3/4]

This is how I have mine now. Not really crazy about having idiot light in head. (That’s header wrap around the wire to try to protect from heat). Would be interested in a stat housing with another hole as Chevyguyase mentioned, but have never seen one or can picture how it would work. Anyone done this? I really need to keep the heater hose attachment, so using that other hole on the passenger side not an option. (Mechanical gauge feed below heater hose)
Thanks
Tom

[67 twins]

Originally Posted by chevyguyase

I have the same coolant sensor hole set up. I can not get a correct reading out of the coolant temp sensor hole in the head. I think because it is to close to the exhaust port. It reads way to hot. I've tried 3 different gauges. I do have my mechanical under dash gauge hooked up to the hole in the head and it constantly reads 250+ degrees. I have to keep my EFI temp sender in the hole in the thermostat housing because I need an accurate input for the ECM. They make a thermostat housing with 2 sensor holes in it, but can't get my hands on one. They also make the part that the thermostat housing bolts to with a sensor hole in it, I can't find one of those either.

Go to 12bolt.com Tom has everything you need for these sixes including the thermostat housings with extra holes. Have one on my 292

[Short 3/4]

Originally Posted by 67 twins

Go to 12bolt.com Tom has everything you need for these sixes including the thermostat housings with extra holes. Have one on my 292

Thanks for the info, will check it out
Tom