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Discussion on 180 Deg VS 195 Deg Thermostats...

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348AMX View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 348AMX Quote  Post ReplyReply Direct Link To This Post Topic: Discussion on 180 Deg VS 195 Deg Thermostats...
    Posted: Aug/09/2007 at 1:46am
What is the general consensus on this, I read many times that 195 in AMC's is best because that is the temperature where the viscosities etc will create the least amount fo friction in the engine, but many people recomend 180 for less chances of detonation etc etc.  What is best on a mildy modified AMC V8 I am most concerned with break in temps at this point but also friction and wouldnt 195 give the least amoputn of potential friction in the cylinders.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote uh60 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/09/2007 at 12:53pm
Just personal opinion on a 68 390, airgap,750 holley,comp 280H cam I have run a 165 degree for several years. don't get hot and roads out nicely after it warms up the airgap makes it very cold natured.
 
Go SOONERS!!!!!!
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote poormansMACHINE Quote  Post ReplyReply Direct Link To This Post Posted: Aug/09/2007 at 1:01pm
If it makes any difference, most of the faster cars I've seen at the track use the higher. They've said they run the best numbers when the engine is close to 200. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Aug/09/2007 at 1:12pm
Originally posted by poormansMACHINE poormansMACHINE wrote:

If it makes any difference, most of the faster cars I've seen at the track use the higher. They've said they run the best numbers when the engine is close to 200. 
Interesting!  I've used both....and not much difference...in my case.....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Aug/09/2007 at 1:16pm
Power output is directly related to the differential between incoming mixture temperature and combustion temperature.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Aug/09/2007 at 1:18pm
Mine overheated or ran on the edge of hot until I put in a 180 superstat. No more issues, runs much better, too. and my engine compression ratio, etc, I need to watch for detonation, so didn't want it to run hot.
You can get too hot, and too cold.
Oil temp isn't necessarily tied that closely to water temp. For example, hyper pistons run a LOT hotter heads than stock pistons, so oil splash against the backside of the head will cause the oil to run hotter, too. Even cooling the water, if the engine is loaded and combustion pressures and temps are high, the oil will be hot.
The thermostat sets the minimum temp the engine runs at, not the max and if your engine is cranking out the BTUs faster than the radiator can remove them, it's going to run hotter than the stat temp anyway.

Why would a 195 stat reduce friction over a 180 stat? You can change oil types and viscosities and do that. It's a little more complex than just raising engine temp as far as oil effeciencies...... Depends on the oil - you can run some oils hotter and get MORE friction because their protective film breaks down, other oil might not. Run the correct oil for the conditions, don't change conditions for the oil, IMO.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 348AMX Quote  Post ReplyReply Direct Link To This Post Posted: Aug/09/2007 at 1:55pm
Originally posted by billd billd wrote:

Mine overheated or ran on the edge of hot until I put in a 180 superstat.
Why would a 195 stat reduce friction over a 180 stat? You can change oil types and viscosities and do that. It's a little more complex than just raising engine temp as far as oil effeciencies...... Depends on the oil - you can run some oils hotter and get MORE friction because their protective film breaks down, other oil might not. Run the correct oil for the conditions, don't change conditions for the oil, IMO.
 
  That is what I dont quite understand 195 is what would be considered normal operating temperature, and the quicker you get up to operating temperature the better because condensation or moisture in the oil will be evaporated so I think that has something to do with the oil integrety if the engine never really reaches operating temps. If you drive your car only on short trips than a higher temp stat is recommended, if you drive your car for long stints than you can get away with a lower temp stat that opens below normal operating temps, because the longer drives will eventually get it to normal operating temps and evaporate moisture.  I dont understand why a lower openning point would cause the engine to run cooler, wouldnt it just delay the normal operating temp of a given engine/combination?
 
  Why not use a 195 with a step colder spark plug?


Edited by 348AMX - Aug/09/2007 at 1:58pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote poormansMACHINE Quote  Post ReplyReply Direct Link To This Post Posted: Aug/09/2007 at 2:19pm
How do you mean delay the normal operating temp?
Thermostats operate in a range of degrees. 158~163(160), 178~183 (180) etc. The advertised number is approximately the center point between the crack of daylight and fully open.
It's up to your radiator to be in proper working order and properly sized to get rid of the heat at the midpoint.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote XJ-001 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/09/2007 at 2:56pm
In theory (so I've been told), the more heat you can retain in the engine the more efficient it will be. THAT BEING SAID, there is a physical limit to this based on the material properties of the engine components (thermal expansion, melting points and such) and the capabilities of the lubricants. IIRC, more than 50% of the energy generated in the engine by the combustion process is lost as heat into the cooling system and out the exhaust.

As for the topic of the original post, the 70 TSM states that ALL 70 AMC engines came from the factory with a 205 degree t-stat. The normal temp range of the factory gauge is 165 to 235 (cold side of green band to hot side). Mid-scale calculates to 200 degrees, but then again, these gauges are notoriously inaccurate. These engine temps also do not take into consideration the poor gas quality of today. The 100 octane gas of the early 70's will tolerate a lot more engine temp than the 92 octane crap we get today...

On my car I run a 180 superstat, 3-row radiator, factory shroud and factory 7-blade flex fan. The factory temp gauge normally reads in the upper third of the green band, but I have not checked it with an accurate gauge. I assume it's running around 200-205 degrees.


1970 AMX 390 4spd

1970 Javelin 390 Auto (Project)

2002 Grand Cherokee Overland Edition

2002 Olds Intrigue (The Other Orphan)

Bloomington, MN
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Post Options Post Options   Thanks (0) Thanks(0)   Quote poormansMACHINE Quote  Post ReplyReply Direct Link To This Post Posted: Aug/09/2007 at 3:07pm
Originally posted by XJ-001 XJ-001 wrote:

The 100 octane gas of the early 70's will tolerate a lot more engine temp than the 92 octane crap we get today...



At the time most of these engines were built,I don't believe they were using the same octane calculation method as "today".
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