temp gauge question

[Day 2 C10]

So I took out my c10 for the first real ride of 25 in its winter tune up. Truck did great no issues just a question as I have a 185 t stat in it (better winter heat) and sitting at the stop light it climbs up to the pictured reading and hangs around there for the most part. what dose this area correlate to on the temp gauge for temp the sender is in the drivers head and the mechanical gauge is in the intake that reads 180-190. I just want to make sure as the gauge in the summer hangs out in the middle with a 5/8 restrictor no t stat

[LockDoc]

Originally Posted by Day 2 C10

So I took out my c10 for the first real ride of 25 in its winter tune up. Truck did great no issues just a question as I have a 185 t stat in it (better winter heat) and sitting at the stop light it climbs up to the pictured reading and hangs around there for the most part. what dose this area correlate to on the temp gauge for temp the sender is in the drivers head and the mechanical gauge is in the intake that reads 180-190. I just want to make sure as the gauge in the summer hangs out in the middle with a 5/8 restrictor no t stat

It would be different for almost every vehicle. If you have or can find someone with a hand held digital temp reader that would be the best way to go. Not sure what you mean by 5/8 restrictor. Are you not using a thermostat?

[Stocker]

What Leon said ^^.

I run a 195* t-stat year round, good heat in winter and no overheat in summer. My needle typically sits to the 'cold' side about the same amount as yours is to the 'hot' side.

I'm curious about the rest of your cooling system. Coolant recovery tank? Shroud? Type of fan?

[Day 2 C10]

Originally Posted by LockDoc

It would be different for almost every vehicle. If you have or can find someone with a hand held digital temp reader that would be the best way to go. Not sure what you mean by 5/8 restrictor. Are you not using a thermostat?

Yes ive done that I have an inferred gun not to mention the snap on inferred tool, the issue becomes this is an aluminum headed Procharged application and with the 1.7/8 header getting a good reading is hard.

The motor in the summer dosen't run a thermostat what we do (very common in racing ) is run a restrictor to allow ample flow through the system

[Day 2 C10]

Originally Posted by Stocker

What Leon said ^^.

I run a 195* t-stat year round, good heat in winter and no overheat in summer. My needle typically sits to the 'cold' side about the same amount as yours is to the 'hot' side.

I'm curious about the rest of your cooling system. Coolant recovery tank? Shroud? Type of fan?

what I have is a 4 core radiator with twin electric 13" fans plus a factory shroud with a 160 fan clutch on a old 426 hemi aluminum blade fan (my off topic stuff is all gen 2 hemis) the grill area is shrouded to force the most air into the rad. the water pump is a moroso short hi flow unit the intake has been modified to have rear to front external lines. Plus it runs a big block style bypass in the front

engine bay pictured (its a 621rwhp street truck at @5500-6000ft elevation)

[LockDoc]

Originally Posted by Day 2 C10

what I have is a 4 core radiator with twin electric 13" fans plus a factory shroud with a 160 fan clutch on a old 426 hemi aluminum blade fan (my off topic stuff is all gen 2 hemis) the grill area is shrouded to force the most air into the rad. the water pump is a moroso short hi flow unit the intake has been modified to have rear to front external lines. Plus it runs a big block style bypass in the front

engine bay pictured (its a 621rwhp street truck at @5500-6000ft elevation)

I wonder if the restrictor isn't slowing down the water flow enough. Especially with the high flow pump. If the water flows through the radiator too fast it will not cool it enough to cool the engine down. I would try installing a thermostat and see what it does.
.

[Day 2 C10]

Originally Posted by LockDoc

I wonder if the restrictor isn't slowing down the water flow enough. Especially with the high flow pump. If the water flows through the radiator too fast it will not cool it enough to cool the engine down. I would try installing a thermostat and see what it does.
.

No no its in a winter tune/ set up now with a thermostat (185) the summer gets the restrictor) that's what the concern is trying to figure out the correlation of the temp gauge to relative temp on degrees just to make sure there is no issues

[Stocker]

Originally Posted by Day 2 C10

what I have is a 4 core radiator with twin electric 13" fans plus a factory shroud with a 160 fan clutch on a old 426 hemi aluminum blade fan (my off topic stuff is all gen 2 hemis) the grill area is shrouded to force the most air into the rad. the water pump is a moroso short hi flow unit the intake has been modified to have rear to front external lines. Plus it runs a big block style bypass in the front

engine bay pictured (its a 621rwhp street truck at @5500-6000ft elevation)

Well shoot, nothing to be gained comparing to my factory stock setup then.

[Rich69shortfleet]

How the gauge reads depends heavily on the sending unit.

If you really want to know how hot it is getting, install a gauge with numbers on it which is specifically calibrated to a sending unit to which it is attached.

[HO455]

After 55 plus years there isn't much correlation between the needle reading and the temperature of the water. For example mine has recalibrated itself twice, when the wire at the sender came unhooked and was bouncing on the intake. This caused the needle to bounce from full to zero almost faster than you could see it. That action caused the needle to move on the shaft. The result was the needle now has a different zero or cold mark. So the normal temperature range indicated changed its location on the guage.

What's more important than the actual number is that the engine consistently runs in the same range on the guage. The guage is there to indicate changes from normal operation. So even though my guage is no longer pointing the way it did when it left the factory it still tells me everything I need to know.

Corrosion in the connections and changes in the sender internal resistance will cause the guage to no longer read the way it was designed. And replacement senders are a crap shoot at best. Some of them are ridiculously out of spec.

[MySons68C20]

Shoot the upper radiator hose with your infrared gun and see what it says.
I find the factory gauges are a vague reference to the actual temp.

[PbFut]

I recently had a issue with a new out of box tstat. Running a efi system give an opportunity to have a digital temp gauge in the head. Placed on right head in rear. The factory temp gauge has its sensor in the intake very close to the tstat. I was having heat issues. Wild swings and no sync between the two. One would be at temp or hot. The other cold. Swapped in a high flow tstat from Speedway and all the issues stopped. Night and day difference. I did note the heater was probably a bit low for cold climate needing a good heater. I rearly venture out if the thermometer is south of 50.

[MikeB]

Good luck with getting accurate readings on a factory-style gauge with an aftermarket sender, because they all seem to have different temp/resistance curves. I came up with this temporary solution to help me choose the proper shunt resistor for the gauge.

Even then, my gauge/sender combo is big-time non-linear. The needle doesn't start moving until 150-160, it's in the mid range at 180-190, but 210 is way right, and anything above that is pegged.

[Accelo]

Pay attention to the comments about the sender.

"How the gauge reads depends heavily on the sending unit."

"If you really want to know how hot it is getting, install a gauge with numbers on it which is specifically calibrated to a sending unit to which it is attached."

Countless guys have been bitten by this trap, including me.
Studies have proven the after-
market stuff has little correlation to the actual temperatures when compared to the service manual information.

This is from davepl, use to be his weekly post;

[Accelo]

For Truck Years: 1974 - 1978

The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 350 Ω
Middle Line when sender resistance = 68 Ω
Right Line (Hot) when sender resistance = 46 Ω

For Truck Years: 1979 - 1991

The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 1,365 Ω
Middle Line when sender resistance = 96 Ω
Right Line (Hot) when sender resistance = 55 Ω

[Accelo]

The picture below compares an original Delco sender to a NAPA replacement. The Delco is on top:

[MikeB]

Originally Posted by Accelo

For Truck Years: 1974 - 1978

The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 350 Ω
Middle Line when sender resistance = 68 Ω
Right Line (Hot) when sender resistance = 46 Ω

For Truck Years: 1979 - 1991

The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 1,365 Ω
Middle Line when sender resistance = 96 Ω
Right Line (Hot) when sender resistance = 55 Ω

That's some really good info. Anything for 67-72?

As for aftermarket gauges with senders, I have found Autometer electric gauges to be very good. I used their Sport Comp water temp, oil pressure, and voltage gauges on two vehicles back when they cost half as much as they do now. I suspect their full-sweep mechanical gauges are even better.