Thermostat question 180 or 160?

64nailhead

Goat Herder
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Dec 1, 2014
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Running 200-210 is not an issue, unless you can’t stop it in that range.
It’s real old school hocus locus that the motor is happy at 170. The best fuel burn (economy) is going to occur above 180 on most engines. The key is consistency, especially with a non electronic carb deal. Mike’s comment has a lot of info - controlling the temps with the fans with a wide open thermostat is the absolute best plan. But, the big butt, is it’s hard to do with a carb imho.
 
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Supercharged111

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Running 200-210 is not an issue, unless you can’t stop it in that range.
It’s real old school hocus locus that the motor is happy at 170. The best fuel burn (economy) is going to occur above 180 on most engines. The key is consistency, especially with a non electronic carb deal. Mike’s comment has a lot of info - controlling the temps with the fans with a wide open thermostat is the absolute best plan. But, the big butt, is it’s hard to do with a carb imho.

Colder water should = colder IAT which means more timing. That, and a running start on overheating ( think truck pulling trailer up a bigass hill) is why I run colder than stock on some stuff. My LS stuff still has factory stats.
 
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64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
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Upstate NY
Colder water should = colder IAT which means more timing. That, and a running start on overheating ( think truck pulling trailer up a bigass hill) is why I run colder than stock on some stuff. My LS stuff still has factory stats.
Agree if you have little to no air flow in the engine compartment. If you have any means of getting fresh air into the carb, then coolant temp isn’t affecting iat’s, but high iat’s can heat up the coolant.
Can only offer guesses though, without good info. Cowl induction hoods are a blessing for crazy under hood temps - they create air flow much better than forward facing scoop if the inner fender are still in.
 
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Clone TIE Pilot

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Aug 14, 2011
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For max engine life you want a 195 T-stant.
Colder water should = colder IAT which means more timing. That, and a running start on overheating ( think truck pulling trailer up a bigass hill) is why I run colder than stock on some stuff. My LS stuff still has factory stats.

But doing that rejects additional out as waste heat instead of going torwards work. The hotterthe engine, the mord powerful and efficient it will be. Look up heat engines and the Carnot cycle.
 
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Supercharged111

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Oct 25, 2019
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Agree if you have little to no air flow in the engine compartment. If you have any means of getting fresh air into the carb, then coolant temp isn’t affecting iat’s, but high iat’s can heat up the coolant.
Can only offer guesses though, without good info. Cowl induction hoods are a blessing for crazy under hood temps - they create air flow much better than forward facing scoop if the inner fender are still in.

You bring up a good point as I'm speaking out of personal experience. My carb'd Crown Vic breathed hot air with an open element filter.
For max engine life you want a 195 T-stant.


But doing that rejects additional out as waste heat instead of going torwards work. The hotterthe engine, the mord powerful and efficient it will be. Look up heat engines and the Carnot cycle.

I've heard that before, hot engines need less advance. . . or do they tolerate less advance? I start losing power onesie twosie on the dyno when my Camaro gets above 210*. I know some of it has to do with overly protective IAT corrective values, but heat soak a boosted motor and tell me it makes more power. Extreme example, yes, but you get my point.
 
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64nailhead

Goat Herder
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Dec 1, 2014
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The rule of thumb I’ve been given is 1 degree out at 135degree iat and one more every 10 degrees. For coolant, I have no idea.
 

Clone TIE Pilot

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Aug 14, 2011
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You bring up a good point as I'm speaking out of personal experience. My carb'd Crown Vic breathed hot air with an open element filter.

I've heard that before, hot engines need less advance. . . or do they tolerate less advance? I start losing power onesie twosie on the dyno when my Camaro gets above 210*. I know some of it has to do with overly protective IAT corrective values, but heat soak a boosted motor and tell me it makes more power. Extreme example, yes, but you get my point.

Generally hotter engines can't take as much ignition timing advance. However, timing advance is a clutch for inefficient combustion chambers. It is why Vortec heads like less advance than previous SBC heads. Running a cold T-stant is a clutch for a clutch basically.

pYjra.gif


Real heat engines will lose some heat to the environment as it transfers from the hot reservoir to the heat engine. An ICE's job is to siphon some heat off to convert to work which equals Qh-Qc.
 
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Supercharged111

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Oct 25, 2019
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Generally hotter engines can't take as much ignition timing advance. However, timing advance is a clutch for inefficient combustion chambers. It is why Vortec heads like less advance than previous SBC heads. Running a cold T-stant is a clutch for a clutch basically.

pYjra.gif


Real heat engines will lose some heat to the environment as it transfers from the hot reservoir to the heat engine. An ICE's job is to siphon some heat off to convert to work which equals Qh-Qc.

Hot engines burn less fuel too, wouldn't that equal less energy?
 

Clone TIE Pilot

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Hot engines burn less fuel too, wouldn't that equal less energy?
Hot engines are rejecting less energy from a given amout of fuel burned as waste heat so more of it is available for work. In other words, hotter engines are more efficient at converting fuel to work and thus use less fuel for a given work output. Rejecting less waste heat causes the engine to run hotter. Running an engine colder means wasting more energy in the fuel as wastd heat rather than using it for work. Moreover, it is impossible to completely convert heat to work as there will always be some waste heat due to the second law of thermodyamics. Most ICE produce 2x waste heat compared to work.
 

64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
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Upstate NY
Ahh, the fine line between fuel economy and power.

Running the engine cooler will allow for more power to be produced, but at the cost of fuel economy. And 99.9% of all motors have plenty of fuel system capacity to cover the additional power produced from the additional fuel used.

So what is better, a 160 or 180 thermostat? I stand with consistency, running a motor at 200 consistently is an easier tune and more fuel efficient than one that varies from 160 to 200 depending in conditions.

Great stuff Clone TIE!!!
 
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