71 temp sending unit - tough question
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Joined: Sep 2001
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From: Middlefield CT
71 temp sending unit - tough question
I have one of the obscure questions:
What is the Ohms resistance range on a 1971 temp sending unit?
I have a new engine that goes like stink, approx 450 Hp. The heads are Proline an the temp hole is small yet the vette's sending unit is large. I found one that fits but it is not giving the proper reading. SO I was thinking that I could alter it's resistance but I need to know the range.
Any Ideas? Or better yet anyone know of a part that will work?
What is the Ohms resistance range on a 1971 temp sending unit?
I have a new engine that goes like stink, approx 450 Hp. The heads are Proline an the temp hole is small yet the vette's sending unit is large. I found one that fits but it is not giving the proper reading. SO I was thinking that I could alter it's resistance but I need to know the range.
Any Ideas? Or better yet anyone know of a part that will work?
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by 71 Red Sled
I have one of the obscure questions:
What is the Ohms resistance range on a 1971 temp sending unit?
I have a new engine that goes like stink, approx 450 Hp. The heads are Proline an the temp hole is small yet the vette's sending unit is large. I found one that fits but it is not giving the proper reading. SO I was thinking that I could alter it's resistance but I need to know the range.
Any Ideas? Or better yet anyone know of a part that will work?
What is the Ohms resistance range on a 1971 temp sending unit?
I have a new engine that goes like stink, approx 450 Hp. The heads are Proline an the temp hole is small yet the vette's sending unit is large. I found one that fits but it is not giving the proper reading. SO I was thinking that I could alter it's resistance but I need to know the range.
Any Ideas? Or better yet anyone know of a part that will work?
You could pick up an IR heat gun and satisfy your curiosity.
Le Mans Master
Joined: Mar 2004
Posts: 7,502
Likes: 1,510
From: Little Rock AR
Not obscure at all. My Dart IE heads had a small hole too. I hogged out the hole with a small cylinder shaped stone in my die grinder then tapped it for the proper pipe thread. You do not need to take much off to get to the proper tap drill size. It is pretty close to the outside diameter of the current threads in your head. I do not have a tap drill chart in front of me but they are out there on the net. Work slow.
Just one way to "get-er-done".
-Mark.
Just one way to "get-er-done".
-Mark.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
you can't alter the one you have. You can use it and make a resistance bridge to possibly get the gauge to read better. There were a couple of threads in here recently about temp senders and gauges, do a search and see if it shows up, there were a couple really good links in there, I thought I bookmarked them but aparently not
edit: Ahh, there ya go, a simple solution, good one Stingers
edit: Ahh, there ya go, a simple solution, good one Stingers
Last edited by SIXFOOTER; Sep 16, 2006 at 08:46 AM.
Racer
Joined: Dec 2005
Posts: 260
Likes: 3
From: Houston TX
try this:
Use a pot of boiling water and measure the temp with a thermometer, in addition use an ohm-meter on the temp sending unit to measure the change in resistance as the temperature rises. You will need to take measurements in increments of about 10 degrees and plot them out. Obviously you won’t be able to boil the water past 105 or so degree so you can linearly approximate to predict what the resistance will be up to the highest temp you think you will reach (hopefully not past 295 or so). You will want to repeat this process a few time to make sure your approximation is correct, but be careful (you will want to cool the sending unit all the way down before retesting to prevent hysteresis. This may be overkill, but it would be fun to see if it worked!
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Joined: Sep 2001
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From: Middlefield CT
errr... uhmmm ... yeah the resistance bridge.. well you see I was driving over the resitance bridge the I notice the Ohm tunnel and I got confused so I took the capacitor ferry. sixfooter only read please (psst I don't know what resistance bridge is)
stinger69 - how did you keep metal shavings out of the engine?
stinger69 - how did you keep metal shavings out of the engine?
Safety Car
Joined: Oct 2004
Posts: 3,725
Likes: 5
From: Minnesota
Here's what I can tell you about my 75. The old sender was a 1/2" unit. My 350 H.O. with vortec heads only has a 3/8" hole. I put in a Borg-Warner Volvo unit #WT510. It reads around 20 degrees warmer than the stock unit but basically does the job. Keep in mind this is for a 75 so I'm not sure if your guage would work off the same parameters. Good luck.
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Joined: Sep 2001
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From: Middlefield CT
Thanks JD. as soon as I start the engine its pins on hot. Hopefully this will help. I wonder how I can reduce/ increase the ohms to get a more correct reading.
If only I paid attention in my high school physics class. Any EE professors out there?
If only I paid attention in my high school physics class. Any EE professors out there?
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Le Mans Master
Joined: Sep 2001
Posts: 7,739
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From: Unreconstructed, South Carolina
It's my understanding that Lectric Limited sells 1/2" NPT senders correctly calibrated for C3 temp gage ... about $20 a pop ... but if you've tussled with mismatched calibration issues you might realize $20 is cheap. Perhaps they also have a 3/8" NPT sender that's calibrated same as their 1/2" NPT ... contact Lectric Limited.
http://www.lectriclimited.com/mainpage.htm
http://www.lectriclimited.com/mainpage.htm
Last edited by jackson; Sep 19, 2006 at 12:32 AM.
Le Mans Master
Joined: Mar 2004
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From: Little Rock AR
Originally Posted by 71 Red Sled
stinger69 - how did you keep metal shavings out of the engine?
-Mark.