During a recent post, 54greg commented "With the new alum car runs 160-180." Greg's comment had me wondering if 160 degrees is too cool for a SBC to run efficiently and it sent me on a search trying to find out the ideal operating temperature range for a small-block Chevy. Many, many sites commented on running at the most efficient operating temperature, but none said just what that ideal temperature is. I finally found this one site that states "Engines are designed to operate within a “normal” temperature range of about 190 to 220 degrees F.", but I'm still wondering if this applies generally to all car engines and does it apply to SBC's?

Here's a link to some that site and the article by the National Automotive Radiator Association (NARSA). I thought that some of you might find it of interest.

http://www.arrowheadradiator.com/pre...m_failures.htm

In closing, I have 2 questions:

1) Is a range of 190 to 220 Degrees F 'ideal' for a Chevy Small Block?

2) Is there such a thing as running too cool and if so, what are the possible results of running too cool?

Thanks for all and any feedback.

- Pat

 

If you run too cold, you get worse fuel efficiency, your motor oil becomes acidic due to not vaporizing the stuff out that needs to be vaporized, and your exhaust system may not last as long due to increased condensation.

180-200 is a good range for carbed motors, 190-210 for EFI motors.

Doug

 

Thanks for the feedback Doug.

- Pat

 

There is lots of information in the archives on this subject.

Here are my beliefs

Keep it simple and use the thermostat temperature that was specified for your car. The Engineers selected the thermostat design for a reason. I think it is a safe assumption that one will not gain something without sacrificing more of something else by simply increasing or decreasing the operating temperature of the engine.

My general understanding is that the rate of cylinder wear increases as engine temperature decreases. Yes modern engines run hotter but that may be due to the use of aluminum (block and heads) or enabled by fuel injection --- I don't know.

Remeber the KISS principle!

so for
1) It may be helpful to better define "chevy small block" I don't think you'll find one answer at this level.
2) Yes - engine wear and possibly decreased fuel economy and increased emissions

Brian

 

Thanks for the feedback Brian. By Chevy Small Block, I was thinking specifically of the C1 & C2 small blocks. I'll recheck the archives.

- Pat

 

Doug is correct that is the operating temps are too low there is not enough heat to burn off excess vapors and they can turn into condensation that will sludge up your oil.

I'd say though that depending on the motor "normal" operating temps can range from 180º - 220º.
Most C1/C2 cars are going to run in the 180º - 200º assuming they have a 180º t-stat and the cooling systems is working correctly and the car is in tune. Most C3's and up are going to run in the 200º - 220º range simply because most came with a 195º t-stat from the factory starting when they started to add all the emission control equipment and they deliberately needed the cars to run at a higher operating temp to help burn off excess HC to pass new federal emission standards.
It doesn't do the motor any harm to run at say 200º rather than 180º.
My '65 L76 with a DeWitts aluminum radiator, 180º t-stat, stock fan/clutch, shroud, etc and in perfect ignition timing tune runs anywhere from 185º to 210º depending on driving conditions (highway or low speed), outside ambient temp, and how hard I'm driving the car.
My' 78 on the other hand runs consistent at 200º - 220º again depending on the above conditions and with or without AC on. This is an original 11,000 mile car with all stock cooling parts and factory 195º t-stat. It simply runs at a higher operating temp because it was designed to. There is no harm to the motor because of that.

 

How Hot Is Hot?


Source:

General Motors Performance Parts
Crate Engines
Frequently Asked Questions

 

Wasn't original equipment SB stat temp 160-170 degrees?

Then as EPA got involved the stat temp went to 180-190 and now 190-200 on the late model engines.

I know one of the first things the guy with GM LS1, LS2, LS3 and LS7 and Chyl Hemi motors do is swap out the 190-200 stats for 160's to gain performance due to EMC starting to retard timeing when engine temp rises and retarded timing leads to even higher temps. 160 seems to cure that.

Our SB engine don't retard timing as it's mechanical controlled. But I believe you can run more timing for more effecient power if you drop the engine temp 20 degrees as that decreases heating of intake air charge giving more dense fuel mixture and less chance of pre-ignition.

I've always ran 160-170 stats in my vettes and will be running 160 stat in both my LS7 and LS3 retro-mod cars.

Also my operating engine oil temp and my water temps are not the same. For some known reason, engine operating oil temp seem to higher than engines incoming cooling temp and in the burn off range for vaporizing the stuff out that needs to be vaporized.

Lot of new performance cars even run oil cooler's to try and control engine temps with stats that prevent oil from flowing until temp rises to point burn off is achieved.

Different strokes for different folks I guess.

If you want to comtaminate your oil and condense water vapor in exhaust pipe, best way is to crank the engine and let it idle, you know like to charge your battery instead of going out and driveing engine so it reaches full operating temps that will burn off harmfull vapors. Then water still accumulates in exhaust as it cools off but nothing like idling temps will.

 

But.....the temperature spec of the thermostat has little or nothing to do with the operating temperature of the engine. It controls how fast it warms up. If your engine wants to run at 190*, it will run there no matter if your thermostat is 160* or 180*. The operating temperature of the engine is controlled by the efficiency of the cooling system....size and condition of radiator, condition of cooling passages, crud in the block, etc. If your engine is overheating in traffic, changing out a 180* thermostat for a 160* won't make any difference. The only time the thermostat would come into play is if the cooling system is super efficient and the normal operating temperature is below the spec for the thermostat. Usually not an issue with C1s/C2s.

 

very true!! The motor will only run at the t-stat temp assuming the cooling system has the capacity to keep it there. If the cooling system has that capacity than running a 160º t-stat would have it running at too low of an operating temp.
since the t-stat only controls the minimum operating temp, not at what temp the motor may eventually go up to or regularly operate at it's main function is to help speed up bringing the motor up to operating temp reducing cylinder bore wear.
I love all the posts from people that say they have overheating issues and they tried swapping in a lower t-stat such as swapping out a 180º for a 160º or they removed the t-stat altogether and wonder why it didn't fix their problem. Putting in a lower temp t-stat isn't going to change anything again unless the cooling system is super efficient, which in most cases it isn't, and removing the t-stat will do nothing except cause longer warm up times unless it's stuck closed in which case the car won't just run hot but will rather overheat quickly from complete lack of cooolant flow.

 

early Chevy small blocks came with 160° tstats for the alky antifreeze.

c2 Corvettes came from the factory with 170° tstats for optimum performance.

as smog controls were added, the tstats moved up to 180° and 195°

Got smog controls on your c2??

PS remember that 160°, 170°, 180°, and 195° are the temps that start the coolant circulating to the rad, not the temp that locks the tstat wide open or the operating temp of the engine. I prefer factory tstat temps specified for the engine in the car. The factory has more money to spend checking these things out than I do.

 

My 63 has a 60 over 327 - 350 hp 160 degree stat
For some reason a brass radiator. A 4:10 gear
Yesterday Afternoon temp outside around 85 degrees at 3000 rpm she run most of the time around 190 with a 215-75x15 tire Whatever that works out

 

67's came with 180* 'stats per Chevy Engineering specs and the '67 AMA submissions. Don't have the pre-'67 Chevy documents, and none of the owner's manuals (or Shop Manuals) list the 'stat spec, but all midyears had exactly the same cooling system.

 

Thanks to everyone for the education on operating temperature ranges. I've saved snippets of everyone's feedback for future reference.

- Pat

 

John, just for reference, I have the specs from Chevrolet on my '65 that came from Chev in the restoration pkg you can get from them. The pages are headlined as the AMA specifications.
In the specs under the Cooling System section, which this particular page is dated Feb. 1965, it lists the themostat info as follows:

Type.......... ............ Pellet
Begins to Open at...... 177º-183º F
Fully opened at......... 212º F

allowing for unit variances if it's Begin to Open range is 177º-183º I assume that the factory t-stat on a '65 is a 180º unit.

 

Back in the '60s my experience was C2 small blocks would run at 180 unless in REALLY slow traffic for a long time, as in a parade at 3 mph. Big blocks ran at 200 most of the time without problems.

Pulling the fan clutch and replacing the heavy steel fan with an aluminum flex fan with more blades would cool them down somewhat.

By the way my '90 Suburban with a built 383 runs 155 almost all the time. Previous 350 registered the same. I think my temp gauge might read on the low side!

 

Page 6s-4 of the 1963 shop manual, "A 170 degree thermostat should be used when permanent antifreeze is used,160 degree thermostat with alcohol antifreeze.'' Don't know about other years

 

My 64 engine is a 327/350 with a 180 tstat. 98% of the time runs at 180. On some of the real hot days it will go to 200 and once in awhile to 210.

 

This thread makes me less nervous about my SBC creeping up toward 200 degrees with a 180 degree thermostat. In Los Angeles traffic (similar to the "3 mph parade" reference earlier) I am frequently trying to find a place where I can cruise in 4th for a while to cool down the engine. I guess maybe I will just relax when the temp is 200 and enjoy the parade.

 

And when you have a NON-OEM style/modified engine in your car, what do you do? Piggy-back on the experience of others, try to determine if your modified engine is similar to something similar to your engine or assess your engine's requirements through a trial and error/process of elimination method.
I have a very healthy SB400 with a modified Rochester FI setup, stock 56 style brass radiator, stock 56 4 blade fan and shroud in the 56 (I have added a single elec fan in front with a switch inside to provide extra air flow as needed). There ain't no such thing as that in a Corvette------------or any other Chevy for that matter! Soooooooooooo, what are the guidelines for selecting a thermostat for my combination??? I used the trial and error method and ended up with a 195 thermostat. It's been like that for at least 10yrs and seems to do just fine. Extended idling in the hot summer can produce temps of 220-230*F, but as soon as the car starts moving and air flow is created through the front, the temp comes down fairly quick. My stock, original 56 gauge stays locked up against the low side of the 200* mark, and I've never noticed any typical symptoms of excessive overheating.
As mentioned above, I'm a believer that an FI engine does fine with a 195* thermostat.
The ONLY common problem I see with an FI engine, is related to the heating of the spider nozzle lines below the plenum. But once fuel flow through the nozzle lines increases and air flow over the lines increases, the erratic engine operation (due to heat) goes away.