Engine Temp
Thread Starter
Intermediate
Joined: Aug 2003
Posts: 32
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From: Mishawaka IN
Engine Temp
When I designed my engine I was very weary about excess heat, everything I read led me to believe that colder is better. Well engine runs about 130, my buddy who is a is a mechanic of 25 years by trade says it is running too cold. He admits that is is not use to the type of engine mod I have. Any thoughts?
Race Director
Joined: Apr 1999
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From: CORVETTE 77 385 C.I. TEXAS
This has been well known for a long time. 180F is considered the min. operating temp. which explains why most cars from many manuf. around the world have a 180F+ thermostat which regulates the min. temp. A 160 can be used sometimes since this is the opening temp- not the temp. it will run like w/ a BBC which generates a lot of heat. A SBC even w/ a 160 in general works fine except in winter. In racing it's typical to block part of the cooling system like the rad. when temps are too low.
A quick search turned up this Short 50 hr. test http://www.carnut.com/ramblin/cool3.html
Note that this is just one chart not the final word- others exist.
A quick search turned up this Short 50 hr. test http://www.carnut.com/ramblin/cool3.html
Note that this is just one chart not the final word- others exist.
Intermediate
Joined: Apr 2009
Posts: 38
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From: Victoria
think about it, have you ever heard someone say, dont accelerate too hard in my car because the engine is cold? so it is fair to say, colder cannot be better, just like people cars have their optimum temperature and above or below that can damage or severely harm your cars statistics (0-62 and so on).
I think if the engine runs too cold, isnt there an issue of cracking or something?
I think if the engine runs too cold, isnt there an issue of cracking or something?
Le Mans Master
Joined: Jan 2006
Posts: 6,506
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From: Butler Pa
Engines are designed with clearances that are only optimal at a specific temperature, which is normally around 180* - 200*. These clearances change as the temperature fluctuates. Any temp outside of that range will cause clearances to be either too tight or too loose.
Team Owner
Joined: Jul 2008
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From: In limbo
St. Jude Donor '13-'15, '17 thru '22
When it comes to cooling system discussions on this forum, there is definitely an issue with crack.
That said, we are all more or less speculating without knowing more about the engine components he is using. If 130 degrees is within the design spec for the heads/block combination he is using, there is nothing wrong with running at 130. I know people will jump up and say that runninng that cool will not allow any water or fuel in the oil to evaporate out, and I say
I have evaporated tons of water at 50 degrees farenheit, gasoline evaporates just fine there too. The "optimal" range thrown around above of 180-200 is good for 1968-1974 Corvettes in stock configuration, but is definitely on the low side for 1975-1982 cars that were made to run hotter. Point being: without knowing more about the specific components the OP used to build his motor, nobody can be sure if 130 is good or not. Even once the components are known, I am guessing that the application would also be important, like, is this a racecar? If so, what kind of racing?
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Le Mans Master
Joined: Jan 2006
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From: Butler Pa
without knowing more about the specific components the OP used to build his motor, nobody can be sure if 130 is good or not. Even once the components are known, I am guessing that the application would also be important, like, is this a racecar? If so, what kind of racing?
No one in their right mind would design an engine to run at 130*. The biggest issue is piston and ring to cylinder wall clearance. If the clearances were set to be correct at 130*, what happens if the motor "overheats" so to speak, and goes to 180* or 190*? It seizes up, because the pistons and rings continued to expand to the point where the clearances became zero.
Of course that's no different than when any engine overheats and goes to 240* or 250*. Hopefully it never happens.
The problem here is, at 130* the piston clearance is going to be more than it should. Sooner or later it's going to collapse the skirts on the pistons.
Team Owner
Joined: Jan 2006
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From: Crossville TN
I have installed a 160 F degree stat in my system at one time...but only so that it would properly regulate at 180 degrees [desert summer weather]. The Chevy small block engine was designed to run around 180 degrees. It can run hotter...it can run cooler. Hotter than that burns more hydrocarbons, but lowers engine life and fuel economy. Lower than that increases hydrocarbons but improves fuel economy [as long as it doesn't get below 150 degrees]. Too cold an engine [below 150 deg] will cause engine wear to increase, also. Late 70's and newer cars run at 195 degrees for EPA/emissions reasons only. But, as that was required by Federal mandate, the ECU's expect to see 195 deg or certain systems don't operate properly (tranny lockup, etc.).
Team Owner
Joined: Jul 2008
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From: In limbo
St. Jude Donor '13-'15, '17 thru '22
Yes. I wish I were sufficiently omnicient on engines that I could state as confidently as others that 130 degree coolant temperature is bad under all circumstances. But I am not, so I will not.
It would appear that you have answered your own question. Your theory sounds good, that an engine is designed to run at a given temperature range and forcing it to run outside that temperature range is a bad idea, you'll get no argument from me on that. However, the original poster said that he designed his own engine. What I don't know is what those design parameters are.
No one in their right mind would design an engine to run at 130*. The biggest issue is piston and ring to cylinder wall clearance. If the clearances were set to be correct at 130*, what happens if the motor "overheats" so to speak, and goes to 180* or 190*? It seizes up, because the pistons and rings continued to expand to the point where the clearances became zero.
Of course that's no different than when any engine overheats and goes to 240* or 250*. Hopefully it never happens.
Of course that's no different than when any engine overheats and goes to 240* or 250*. Hopefully it never happens.
Team Owner
Joined: Jul 2008
Posts: 23,419
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From: In limbo
St. Jude Donor '13-'15, '17 thru '22
Last year, I had an overtemperature problem, so I pulled out my 180 thermo and tested it. It didn't even start opening until 195 and wasn't fully open until 205, so I decided I didn't want that one in my car at that time, even though it was technically "working". I got a 160 that started to open at about 165 and was fully open at 170 and put it in. Contrary to a lot of beliefs here, there is nothing wrong with doing that.
For those who would bash me again, I'll note: during winter storage, I got a 180 thermo that starts opening right at 180 and is fully open below 190 and installed it in my car.
I am not aware of any advantage to running a cooler thermostat. I only did it to be certain I took one component of the system off the table when diagnosing a problem. In the majority of cars, changing to a cooler thermo will have little or no impact on the operating coolant temperature. Those who are changing one working thermostat for another to try to get their car to run cooler are more than likely wasting their time and money.
Team Owner
Joined: Jan 2006
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From: Crossville TN
The only 'advantage' is that the 160F stat opens sooner than the 180F stat. In very high temp environments, that allows the engine to stabilize operating temps more gradually...and can prevent it from becoming hot enough that it can't recover with the cooling capacity available with a specific vehicle. If the cooling system is as was originally intended (clean, open hoses, good 50/50 antifreeze mix, all seals in place and in good condition, etc., etc.), that shouldn't be necessary. But, in my case, all of the shroud seals were shot and the lower shroud extension piece was missing; so I had an 'uphill climb' to keep the car cool in 115F degree weather with my A/C running. I found that to be a problem with the 180F stat; but after putting the 160F stat in it, the car was marginally acceptable. I have since redone all of the seals and am looking for an [affordable] lower shroud extension piece to complete the system. {I also moved to middle Tennessee...no 115F days here!} 
P.S. Anyone telling you that going to a lower stat can not allow any improvement for an individual vehicle is
. For the general population of C3's, they may well be correct; but for a specific situation...no one is that smart. 
P.S. Anyone telling you that going to a lower stat can not allow any improvement for an individual vehicle is
. For the general population of C3's, they may well be correct; but for a specific situation...no one is that smart.