Temp gauge issue
Thread Starter
Racer
Joined: Apr 2015
Posts: 412
Likes: 12
From: Carrollton, Georgia
Temp gauge issue
Trying to get the temp gauge working properly in my 77, and thought I had it. I started the car. I have a mechanical gauge to the head and the stock gauge to intake (sending units) Well they both started working and moving up. Once the engine got to about 205, both gauges were reading 205, so I was happy, but when the thermostat opens and the Mechanical gauge goes down to about 160-170, the stock gauge does not. Any ideas?
Race Director
Joined: Oct 2008
Posts: 19,147
Likes: 1,667
From: Long Island
One gauge is closer to the return from the radiator, the other is closer to the feed to the radiator - engine to radiator hose. I would check the readings with a digital gauge to be sure. That is my best guess.
I get a 10 degree difference between the head and the manifold on my 71. High flow stat and spotless internals on the engine - just rebuilt.
I get a 10 degree difference between the head and the manifold on my 71. High flow stat and spotless internals on the engine - just rebuilt.
Thread Starter
Racer
Joined: Apr 2015
Posts: 412
Likes: 12
From: Carrollton, Georgia
I understand that but if the gauges stays the way it is, I'll never know if the t stat is working basically
Thread Starter
Racer
Joined: Apr 2015
Posts: 412
Likes: 12
From: Carrollton, Georgia
One gauge is closer to the return from the radiator, the other is closer to the feed to the radiator - engine to radiator hose. I would check the readings with a digital gauge to be sure. That is my best guess.
I get a 10 degree difference between the head and the manifold on my 71. High flow stat and spotless internals on the engine - just rebuilt.
I get a 10 degree difference between the head and the manifold on my 71. High flow stat and spotless internals on the engine - just rebuilt.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,850
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Trying to get the temp gauge working properly in my 77, and thought I had it. I started the car. I have a mechanical gauge to the head and the stock gauge to intake (sending units) Well they both started working and moving up. Once the engine got to about 205, both gauges were reading 205, so I was happy, but when the thermostat opens and the Mechanical gauge goes down to about 160-170, the stock gauge does not. Any ideas?
The senders have a wide margin for error when ascending from heat too. When we tested the senders years back the ohms going up varied from the ohms going down but they always came down eventually.
You might try a different sender and see if this corrects the issue.
Willcox
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
You won't know "when" the T-stat is opening. But you will know that it IS opening properly, because it levels off at acceptable running temperature. If the stat did not open, your engine temps would quickly climb to 240*F or higher.
Thread Starter
Racer
Joined: Apr 2015
Posts: 412
Likes: 12
From: Carrollton, Georgia
It could be a combination of things.. Location of the sender, the fact that the mechanical gauge is going to read more responsive than the electrical gauge and possibly an issue with the sending unit.
The senders have a wide margin for error when ascending from heat too. When we tested the senders years back the ohms going up varied from the ohms going down but they always came down eventually.
You might try a different sender and see if this corrects the issue.
Willcox
The senders have a wide margin for error when ascending from heat too. When we tested the senders years back the ohms going up varied from the ohms going down but they always came down eventually.
You might try a different sender and see if this corrects the issue.
Willcox
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Thread Starter
Racer
Joined: Apr 2015
Posts: 412
Likes: 12
From: Carrollton, Georgia
Wilcox, the sending unit I got was the one that advanced auto parts said was stock for the the 77 Corvette. It looks like a 3/4 npt. Thing is, my heads only have half or 3/8 threads. Any suggestions. Also do you sell sending units that are for sure the correct ohms for the 1977 year?
Thread Starter
Racer
Joined: Apr 2015
Posts: 412
Likes: 12
From: Carrollton, Georgia
I understand that. But what I don't like is the idea that my gauge is telling me im driving around at 205, and in reality I'm driving at 165
Team Owner
Joined: Jul 2006
Posts: 22,141
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From: Kannapolis NC
Team Owner
Joined: Jul 2006
Posts: 22,141
Likes: 4,156
From: Kannapolis NC
Thread Starter
Racer
Joined: Apr 2015
Posts: 412
Likes: 12
From: Carrollton, Georgia
If that is the case, then wouldn't the Mechanical gauge not go up to 205-210, then drop quickly to about 165-170 after a few minutes?
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,850
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Wilcox, the sending unit I got was the one that advanced auto parts said was stock for the the 77 Corvette. It looks like a 3/4 npt. Thing is, my heads only have half or 3/8 threads. Any suggestions. Also do you sell sending units that are for sure the correct ohms for the 1977 year?
I make an adjustable resistor that will dial the dash unit to match the sender. https://willcoxcorvette.com/corvette...resistor-77-82
I also make a 3/8 version of the sender that will fit your heads. However we make the one to two at a time so they are a bit on the pricey side. https://willcoxcorvette.com/corvette...79-3-8-npt-new
Willcox
Thread Starter
Racer
Joined: Apr 2015
Posts: 412
Likes: 12
From: Carrollton, Georgia
The sender is probably stock but the ohms won't read correctly regardless of where you get the sender. Some will be closer than others though. But the aftermarket heads all have 3/8"npt threads for the senders and unless you have another place to screw in the stock sender you'll need one 3/8"
I make an adjustable resistor that will dial the dash unit to match the sender. https://willcoxcorvette.com/corvette...resistor-77-82
I also make a 3/8 version of the sender that will fit your heads. However we make the one to two at a time so they are a bit on the pricey side. https://willcoxcorvette.com/corvette...79-3-8-npt-new
Willcox
I make an adjustable resistor that will dial the dash unit to match the sender. https://willcoxcorvette.com/corvette...resistor-77-82
I also make a 3/8 version of the sender that will fit your heads. However we make the one to two at a time so they are a bit on the pricey side. https://willcoxcorvette.com/corvette...79-3-8-npt-new
Willcox
Melting Slicks
Joined: Feb 2006
Posts: 3,105
Likes: 96
From: Sunrise FL
Thread Starter
Racer
Joined: Apr 2015
Posts: 412
Likes: 12
From: Carrollton, Georgia
blehhhh. Might say forget it and buy autometers..
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,850
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Here is a video on how we did this... and why the adjustable resistor we make is awesome.
65-67
68-76
1977-1982
Last edited by Willcox Corvette; Apr 7, 2016 at 05:02 PM.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,850
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Willcox