[Formulabruce]

I agree with transamric, however, we need to look at a couple things
1. Steve that link to article is for a small block Corvette, look at the picture at the bottom with the teflon tape mythbuster!!
3. That said, the resistance in the GM sending units for guages was made to work where there was alot of heat sink, IE water around it in the top of the intake. I ran a 71 with guages and it always seemed hot, tried new senders, even letric, and similar results, then I moved the sender to the the intake for yuks, and put an infrared gun on it and bam it worked well, and correct'
4. These units for switching on an idiot light from the head, or turning on fans in newer cars work fine and head temp ALWAYS leads engine temp, unless ya own a 3rd gen LT-1. That said, I have never been able to nail down the guages correctly even with new GM sensors way back in 78 when my neighbor brought his pontiac over.
5. Conclusion, the senders from letric work perfect for 70-73 cars factory guages if you put the sender in the intake, by the thermostat, ( spark unit location on some)
I looked for a spec on the actual debth for the sensors of=r the actual length of them, and actually used a small extender in the head once, which I thought would be good but it heats up and no way to cool the metal, not enough water. Finally I firmly believe that GM had in mind using these in the intake for readings, look at their design, they are so close to hot metal near only 2 cylinder in a head .
If you get a sender for guages to read that your engine is at 180, and the sender is in the head, your probably running at a dynamic ( t stat open) temp of 160 . The thermostat is designed to control engine temp, makes logical sense to read the temp there.. I battled this on non chevy,GMC stuff for a bunch of years
PS not trying to stomp on any toes here....

[njsteve]

OK, just got the original, vintage 1513321 temp sender from 70RAIII, here is the updated chart:

80 degrees: Wells at 650 ohms, LL at 573 ohms, GM at 549
90 degrees: Wells at 526 ohms, LL at 445 ohms, GM at 524
100 degrees: Wells at 429 ohms, LL at 365 ohms, GM at 409
110 degrees: Wells at 328 ohms, LL at 266 ohms, GM at 365
120 degrees: Wells at 283 ohms, LL at 227 ohms, GM at 323
130 degrees: Wells at 250 ohms, LL at 200 ohms, GM at 272
140 degrees: Wells at 216 ohms, LL at 170 ohms, GM at 227
150 degrees: Wells at 198 ohms, LL at 155 ohms, GM at 195
160 degrees: Wells at 173 ohms, LL at 133 ohms, GM at 175
170 degrees: Wells at 157 ohms, LL at 119 ohms, GM at 157
180 degrees: Wells at 135 ohms, LL at 101 ohms, GM at 140
190 degrees: Wells at 120 ohms, LL at 89 ohms, GM at 125
200 degrees: Wells at 109 ohms, LL at 79 ohms, GM at 109
212 degrees: Wells at 104 ohms, LL at 75 ohms, GM at 102

Looks like the Wells sender is pretty darn close to the original GM sender's specs. I'd say it's a dead-on match given my pot of hot water on the stove, scientific method.

[Formulabruce]

Steve, so if you put it in the head, and your gauge reads correct, what is the actual engine temp at the T stat with an IR gun? does it match???

[Pepi]

Originally Posted by Formulabruce

Steve, so if you put it in the head, and your gauge reads correct, what is the actual engine temp at the T stat with an IR gun? does it match???

I would like to know also, thanks for all your work Steve, great documentation!!! :

[njsteve]

Originally Posted by Formulabruce

Steve, so if you put it in the head, and your gauge reads correct, what is the actual engine temp at the T stat with an IR gun? does it match???

My wedding anniversary is on Sunday in case anyone wants to buy me one, so I can check for you guys.

:-)

(One of these days I need to get one of those infra red contraptions)

[Lloyd-TX]

Originally Posted by njsteve

My wedding anniversary is on Sunday in case anyone wants to buy me one, so I can check for you guys.

:-)

(One of these days I need to get one of those infra red contraptions)

Congrats on your upcoming anniversary, Steve.
So - how long have you been "shooing her out of the kitchen"?

By the way, those infared thermometers are downright inexpensive these days. I'm fairly certain you can buy a name-brand one with the laser pointer for under $80.

[njsteve]

17 years of borrowing her kitchen utensils for automotive use. Hey, maybe I can get her the infra red tester as a kitchen device for testing the oven temp for accuracy.

Hey, Honey look what I got for you!.....

[Formulabruce]

Originally Posted by njsteve

17 years of borrowing her kitchen utensils for automotive use. Hey, maybe I can get her the infra red tester as a kitchen device for testing the oven temp for accuracy.

Hey, Honey look what I got for you!.....

wow, men with more imagination than me!!
Ill click off 20 years this wednesday, and I bought her something she has always been wanting... a Pontiac....
Solstice now I dont see her as much, and the garage actually has more room minus a car thats being driven hehe

[70RAlll]

Originally Posted by Formulabruce

I agree with transamric, however, we need to look at a couple things
1. Steve that link to article is for a small block Corvette, look at the picture at the bottom with the teflon tape mythbuster!!
3. That said, the resistance in the GM sending units for guages was made to work where there was alot of heat sink, IE water around it in the top of the intake. I ran a 71 with guages and it always seemed hot, tried new senders, even letric, and similar results, then I moved the sender to the the intake for yuks, and put an infrared gun on it and bam it worked well, and correct'
4. These units for switching on an idiot light from the head, or turning on fans in newer cars work fine and head temp ALWAYS leads engine temp, unless ya own a 3rd gen LT-1. That said, I have never been able to nail down the guages correctly even with new GM sensors way back in 78 when my neighbor brought his pontiac over.
5. Conclusion, the senders from letric work perfect for 70-73 cars factory guages if you put the sender in the intake, by the thermostat, ( spark unit location on some)
I looked for a spec on the actual debth for the sensors of=r the actual length of them, and actually used a small extender in the head once, which I thought would be good but it heats up and no way to cool the metal, not enough water. Finally I firmly believe that GM had in mind using these in the intake for readings, look at their design, they are so close to hot metal near only 2 cylinder in a head .
If you get a sender for guages to read that your engine is at 180, and the sender is in the head, your probably running at a dynamic ( t stat open) temp of 160 . The thermostat is designed to control engine temp, makes logical sense to read the temp there.. I battled this on non chevy,GMC stuff for a bunch of years
PS not trying to stomp on any toes here....

I put an LL unit in the intake drivers side of water neck(OEM Position on 71 HO models) and it ran hot by 20 degrees or more. I still say, find an original one and use it. That is the only one that will work correctly with your guages. This friend of mine has 3-4 more used ones(at least he did last week).. He may sell them outright or ebay them..Just PM me guys.. I will see if he will sell any more outright..