In the past there has been conflicting discussion conncerning the use of a 160 degree thermostat. Some seem to think it is counter productive. Anyone have facts or figures or comments on this subject.

Thanks

 

There is an excelent artical in the last "Corvette Fever" magazine on tuning, the ecm and such. In it, it discusses it use of lower temperatures and the harm it does to the setup.
Find a copy and read the artical. I'm thinking of removing my 160degree stat.

 

Howdy Rich - I happen to have the magazine that Strike3 is referring to and was holding it for you - some great reading/reference for tuning on your car!!

Al T

 

http://www.carnut.com/ramblin/_cool3.html

 

Jesus F'ing Christ, run a search

 

We were talking this over this last weekend.... I agree, 180 is better for our cars!!!

 

can i ask something about stats!
when i got my vette i have no idea what has been done it. so when i saw the stat houseing leaking some i got a 195 stat and put it in, since then i have found my fan comes on at 170. so should i change the stat to match the fan coming on at 170? or will the 195 stand up to this opening and closeing, feel perssure in the up hose all the time, not sure if thats good or not? but it maintains 180 most of the time.

 

The dufus that owned your vette before you installed a 160 stat and had the fans reprogrammed to come on at 170 thinking that his operating temp would be lowered.......it wasn't ! C4's that came with 195 stats have their fan come on at 228 F and the auxiliary fan comes on at 238 F.
For the life of me I cannot understand why anyone would think that a 160 F thermostat would allow the engine to run any lower temp except in the winter when the low outside air temps allow the radiator to greatly get rid of heat. Idling and in summer temps, the OEM radiator was designed to attempt to maintain 195 F.

 

 

I read the article, and for the most part agree.

But, it should be pointed out that the LT1/LT4 engine uses a "reverse flow" cooling system.
So, the stock/OEM 180 degree thermostat is situated where the coolant enters the engine. For most engines, 180 degrees on entry equates to 195 degrees on exit (after the coolant picks up 15 degrees from the engine). And, the coolant picks up much of the heat in the heads -- that is where the coolant goes first.
Therefore, the coolant in the block is hotter than the coolant in the heads. And that hotter coolant equates to a hotter block/rings where the heat is needed for longevity.

My '92 LT1 has had a 160 degree themostat in it since 20K miles. Since the 160 thermostat, my fans have been programmed to turn on at 195 rising and turn off at 185 falling. In the winter (in Florida), the lowest digital temperature reading I see is about 172 degrees. So, that equates to 160 degree coolant entering the heads and picking up 12 degrees by the time the coolant reaches the coolant temperature sensor (the digital coolant temperature sensor is located where the coolant goes back to the radiator).
I know when I took it apart at 50K miles to put heads and a cam in it, there was no ridge on the cylinder walls and they still had a "cross-hatch" pattern. I don't think my engine was worn much with a 160 degree thermostat.
But, one engine does not prove longevity. Maybe mine is an accident.
Maybe the reverse flow keeping the block warmer than the heads allows for a 160 degree thermostat better????

However, for a conventional flow engine, I do agree with the article.
I am not suggesting anyone use a 160 thermostat.


Tom Piper

 

Exactly right.. Last time I said that someone called me assbackwards.

You have 2 heat exhangers here.. the radiator and the engine.

fan speeds control radiator temp with ambient air

thermostat controls engine temp with radiator coolant temp.

 

actually my 86 stat was a 180 and thats what i took out since i had no idea how old it was, the parts place gave me a 195 since thats what it calls for. but my fan comes on at 170 by the dash temp gauge. should i put a 180 back in or leave the 195 alone?

 

Tom, I think you are 100% correct. I should have made a distinction between LT1 and L98, but didn't since the link I posted was directed at the original post, who has an '85.


i believe you fan was re-programmed a bit early (or do you have a low-temp fan switch installed?) with that 180 t-stat, the fan should come on at about 190*, not 170*. i would get that addressed, as well as putting another 180* stat back in, now that the winter months are close and you live in the northeast.

 

If you do not believe that lower coolant temps bring enhanced performance from your L98 just run a 160deg T-stat, open the high pressure connector in the A/C line to run the main fan all the time and go down the track. Then reconnect the high pressure connector, let your car idle up to say 195-200deg F and make another pass. Compare trap speeds and answer the question once and for all in your own mind. I've compared time slips and so run the 160deg T-stat & fan switch.

Since your fan's come on now at 170deg F install a 160deg T-stat. While cruzin on the highway the fans will not run but in town they will come on and cycle around the 170deg temp. With a 180deg T-stat I would want my fans to come on around 185-190. The idea is to have fans cycle around the T-stat temp so that they do not run all the time and yet maintain engine temps close to the T-stat setting.

If you are running steep gears or otherwise elevating RPM you may find it difficult to maintain lower engine temps. I've seen an example of this while out on Vette curizes and running the twisties on mountain roads in 2nd gear at 3k-4k RPM.

BTW, my '88 runs a 160deg T-stat and runs close to that with ambient in the 70s or below; when air temps climb into the 90s she will rise to mid 170s. At the strip I sometimes have to run the heater on max to maintain 160-165 for low temp launches.

If your engine cannot maintain 160-170deg coolant temps in 70s-80s air temps you need to check out the cooling system and maybe base timing and tune up issues.

 

o.k. i have a 195 stat in now, and the fan comes on at 170.
and i want to get a 180 stat back in, then how do i change the fan coming on at diff temp? it a 1986. is it in the ECM prom? or on the engine, or rad some were?

 

If its the main fan coming on at 170, and not the auxiliary, then you either have had someone wire something to the main fan, or the chip has been reprogrammed.

 

Look for a sensor in the block below the #1 & #3 spark plugs with a wire running over to the LH harness.
If you find on such sensor the EPROM is programmed to bring on the fans.
If you find such a switch follow the wire to see if it's spliced into the main fan relay.

 

o.k. i will look. i did find the sensor for the temp gauge on the right bank of the engine just forward of #8. i also have a green wire coming out of my fan going up to the top right side tank of the rad. is that suppose to be there? and i only have one fan.

 

Wire in radiator is low coolant sensor.
One fan = controlled by ECM.

 

The wire going to the rad is it between the trans lines?
If so that is a low level indicator switch, I didnt think the low level came into play until 86.