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I am wanting to install a 160 deg f T-stat and also will have my PCM reprogrammed.
The issue im having is that I am testing the thermostats out of the box, and I find they open closer to 170 deg f. So far I'm on my second.. they have both been Motorad 160 deg fail open (premium). Third is on its way.
I am suspending them in water and using a very acurate temp probe. I am heating slow to allow the tstat to get to the temp of the water.

Should I expect a tstat to open closer to 160deg f?
If 167 F is the lowest i can get the Tstat to open. Should this info be co-ordinated to the PCM programmer to have the fans work with the Tstat? Probly going to go with
PCMperformance.
 

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These thermostats work on chemical expansion. It is normal from what I have read to not see full opening at the stamped temperature. It should be fully open by 10degF over the specified value. It will not follow the same curve when closing again due to the chemical/mechanical action.

The other way to look at this is if the thermostat does not spring open or closed at temperature X is this:
The engine will never stay at a specific temperature long when heating up. It will "blast past" 160 quickly unless the fans cut in (assuming summer like outside temperature). Unless it is very cold outside the only way the thermostat will close is if the engine has been shut down for a while.
 

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160 thermostat BEGINS to open at 160. Then slowly open/close as motor temps rise/fall.
 
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Mine definatly was closed untill 166 167 deg, then began to open.
This is a test under special conditions.
1. I suggest it might preform differently with the coolant pump pushing on the valve.
2. Your test does not mimic the near unlimited flow of hot coolant passing the chemical bulb.

I do not think there are many manufactures of 160 thermostats. So you have a choice: use the "160" or use a 180 or 195 that will open at a higher temperature.
 

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I though it was odd to have both act the same but not how I expected.
Most of us would expect some opening close to 160.

The problem is if two respond identically there is a low probability you will find one from another batch that is better.

The part is special specification (non stock) made only for b,d,f body cars 1993-1997 I doubt they make them often, and they sit in the warehouse a long time.
 

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I am wanting to install a 160 deg f T-stat and also will have my PCM reprogrammed.
The issue im having is that I am testing the thermostats out of the box, and I find they open closer to 170 deg f.
So far I'm on my second ... they have both been Motorad 160 deg fail open (premium). Third is on its way.
I am suspending them in water and using a very accurate temp probe.
I am heating slow to allow the tstat to get to the temp of the water.

Should I expect a tstat to open closer to 160deg f?
Like they've been saying, a 160F thermostat BEGINs to open @ 160f.
It may open later if it's not subject to H2Opump operating pressure, like in a pot of boiling H2O.
They all said it better, I'm just agreeing wholeheartedly.
 

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Definitely editorializing here, but genuinely interested in the desire to lower the TS. It was a favored mod as far back as the initial HYPERTECH PPP reprogrammers that included a replacement TS. However, our LT1 is consistently reported as performing optimally at its originally designed temperatures. Near-fanatic scheduled periodic maintenance including coolant flushes and inspection/replacement of relays, wiring and motors pretty much eliminates overheating as a motivator for a lower TS. Having owned three tri-9 B/D cars I've replaced a total (3ea.) fan motors and repaired one instance of a burnt harness, and I'd pour any $$$ I could into making certain those issues are attended v. changing the TS. So again, just curious. This was on a Fleetwood at just 65k miles, with the relays factory mounted outside the fuse box for improved ventilation:
Motor vehicle Automotive tire Automotive lighting Automotive design Automotive exterior


Automotive tire Automotive fuel system Motor vehicle Automotive design Wheel
 
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Most of us would expect some opening close to 160.

The problem is if two respond identically there is a low probability you will find one from another batch that is better.

The part is special specification (non stock) made only for b,d,f body cars 1993-1997 I doubt they make them often, and they sit in the warehouse a long time.
They also fit late model Vortec 5.7 engine used in GM truck/vans.
 

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They also fit late model Vortec 5.7 engine used in GM truck/vans.
Gates and Motorad do not show those applications and I checked several sources. Maybe their data base is corrupt?

Could you provide a link that does show which year, model, engine shares the LT1/L99 thermostat?
 

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If 167 F is the lowest i can get the Tstat to open.
Should this info be co-ordinated to the PCM programmer to have the fans work with the Tstat?
Probably going to go with PCMperformance.
Long story too short:
It's perfectly fine & more than good enough to use 'typically improved '180F tstat fan on thresholds with a 160F tstat.
There are very few circumstances where lower fan-on thresholds become NECESSARY, and there are more tradeoffs.
Those who use 160F tstats are usually willing to accept the tradeoffs once they know them.
If you tell a programmer you are using a 160F thermostat, that's usually enough info to know where to set the fan-on thresholds, unless you think your car works or plays harder than normal by enough to mention that to the programmer as well.
 

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There is no thermal / mechanical advantage to turning the fans on before the thermostat is FULLY open.
(The temp at which it begins to open is obviously colder than when it is FULLY open.)
(The variation between individual MotoRad thermostats is close enough to ignore.)
Otherwise the fans are wasting work against a (partially-to-fully) closed thermostat.

Used to own and daily drive an LT1 wagon for 15 years.
Usually drove it like a meth'd up cabbie.
Learned many details about how the cooling system runs with both 160F & 180F thermostats.
Used a 160F tstat about 8-9 months out of every year - spring, summer, fall.
To improve AC performance, wanted to see how low I should lower my fan-on thresholds.
No matter how I cold or hot I set the fan-on thresholds, I could never get the H2O pump temp sensor to consistently report under
178F
As in, never colder than 178F, with a 160F tstat, and the AC permanently on.
(Exception - only got it under 178F with aggressive DFCO thresholds, and then only coasting downhill, and then only in Nov when it was cold enough out to reinstall the OE 180 tstat.)
Setting the radiator fan-on threshold at or under 178F is setting them to be constantly on, once the thermostat opens.
It's a waste of fan motor service life.
It may also endanger fan motor wiring, especially if it not yet upgraded.
 

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MOTORAD 265180 Specifications ('98 L31)
Bypass Diameter 1.09 in
Bypass Length 1.37 IN
Flange Thickness 0.06 in
Gasket or Seal Included Yes
Gasket/Seal Material Rubber
Gasket/Seal Material Rubber
Installation Tool Included No
Jiggle Pin Weep Hole Yes
Number of Seals 1
Sealing Flange Outside Diameter 2.12 IN
Temperature 180 Deg. F
Temperature (Degree) 180

MOTORAD 307180 Specifications ('96 LT1)
Bypass Diameter 1.18 in
Bypass Length 1.45 IN
Flange Thickness 0.05 in
Gasket or Seal Included Yes
Gasket/Seal Material Rubber
Gasket/Seal Material Rubber
Height 2.16 IN
Height Between Flanges 1.51
Installation Tool Included No
Jiggle Pin Weep Hole Yes
Number of Seals 1
Seal Type O-Ring
Sealing Flange Outside Diameter 2.13 IN
Start to Open Temperature 180 F
Temperature 180 Deg. F
Temperature (Degree) 180

Close enough to easily pass as fraternal, but not quite identical twins ...
 

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Guess I'm not seeing why to bother making seperate applications only a few hundredths of an inch different. The springs look slightly different. But ,how different are they in reality? I did notice some 170 versions ,and may look into them as a compromise. Also to study the two applications from same mfg. up close. Could have sworn they were the same.
 

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Blah blah blah....I love my 160 thermostat, have no issues with it,my fans are not constantly coming on unless your just sitting there idling and not moving where the 180 thermostat will do the same.my engine runs great and i like the fact my engine is not running hot all the time specifically at summer,to me it extends engine life gasket life,ect...heat is a killer....but that's my OPINION, I don't know $hit at the end of the day I've only owned 10 of them lol
 

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... I love my 160 thermostat, have no issues with it.
my fans are not constantly coming on unless you're just sitting there idling and not moving where the 180 thermostat will do the same.
Fan-on thresholds set optimally for a 180F thermostat work well (if not quite optimally) with a 160F thermostat.
... my engine runs great and i like the fact my engine is not running hot all the time specifically at summer, to me it extends engine life gasket life, ect ... heat is a killer ... but that's my OPINION, I don't know $hit at the end of the day I've only owned 10 of them ...
For those LT1 cars (B- D- F- or Y-) that do not experience 'winters' per se, the 160F thermostat is a valid alternative for harder driving enthusiasts, in terms of longevity and durability.

In my experienced opinion, in cold winters:
the 180F thermostat is worth a few MpG over the 160F in cold winters
the cabin heater works better with a 180F or a 195F thermostat for the winter than with a 160F

Cars that never experience ambient temps under 41F / 9C, driven enthusiastically by enthusiasts, do well with the 160F thermostat.
 
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Another low-buck mod for those with 160/180 stats is removing airdams around Thanksgiving.
Result(s) being warmer heater/defroster operation in colder winter weather.
Plus retaining it's heat longer.
 
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