# Running too cool



## 69 237 (Feb 18, 2018)

I got a new 2.5in dual exhaust from pypes and now my motor is running too cool. The only change is the exhaust. Before if left idle it would creep up to 205-210 within 15min. Although it's only been 60-70F outside so far, it only gets up to 180F and that's after I've driven it for 40min and let it idle for a while. 

As soon as I start driving again it instantly goes back to 165F-170F. Never any higher through town or 55mph highway (2000-2200rpm). 

The coolant is a touch strong of a mixture and is an inch or two over the stock cold mark in that 1968 brass radiator. I did install a flowkooler impeller pump with a really close gap between the pump and plate ~0.015".

Any thoughts on why or how to get this back up? Are my mufflers too free flowing?


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## PontiacJim (Dec 29, 2012)

69 237 said:


> I got a new 2.5in dual exhaust from pypes and now my motor is running too cool. The only change is the exhaust. Before if left idle it would creep up to 205-210 within 15min. Although it's only been 60-70F outside so far, it only gets up to 180F and that's after I've driven it for 40min and let it idle for a while.
> 
> As soon as I start driving again it instantly goes back to 165F-170F. Never any higher through town or 55mph highway (2000-2200rpm).
> 
> ...



Do you realize you have a thing called a thermostat? This can regulate engine temps. From what I read, I would say you have a 160 degree T-stat. My opinion, it is perfect. But if you insist throw a 195 T-stat in it and see what the temps do.


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## 69 237 (Feb 18, 2018)

Of course. I have a 195 F thermostat. I verified opening temp when I installed it 2 summers ago. Maybe the thermostat is stuck. I'll replace it and see.

Do you use a lower temp thermostat? I know many, including cliff ruggles, insist on a 195F thermostat to ensure a proper A/F mix.


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## PontiacJim (Dec 29, 2012)

69 237 said:


> Of course. I have a 195 F thermostat. I verified opening temp when I installed it 2 summers ago. Maybe the thermostat is stuck. I'll replace it and see.
> 
> Do you use a lower temp thermostat? I know many, including cliff ruggles, insist on a 195F thermostat to ensure a proper A/F mix.



OK, you did not state you had a 195 T-stat. Yes it is possible that it may be hanging open. It is also possible your gauge may not be reading correctly.

Before pulling the T-stat, you might consider one of the laser temperature guns sold at any auto parts store. They are fairly accurate and you can shoot at different points on the cooling system. My '73 Plymouth temp gauge constantly indicates the engine is near to a boil over in stop and go traffic. Has a huge radiator and the car was never puking any coolant into the overflow - which it should have. Laser temp gun proved my coolant temp was actually very good and my gauge was the problem.

T-stat choice is in my book one's preference or opinion. I read that your oil needs to reach a certain temp to evaporate any moisture in the oil. Hmmm. Might be a case for that if you do short trips around town and don't run the car hard. The 195 T-stat is also mandatory if you live in the snow belt if you want your heater to blow hot air to keep you warm or defrost the ice & snow off your windows.

Never heard the A/F mixture argument - new one on me. Seeing there is an exhaust crossover that goes under the carb and is typically left unblocked, there is a lot of unregulated heat that never sees coolant and no doubt would change A/F ratios as exhaust temps constantly rise and fall based on the heat of the day, under hood temps, and the heavy right foot that exercises combustion heat which is whisked away out the exhaust and its crossover under the carb.

A cooler running engine can lessen the chance for detonation or engine pinging, allows more timing advance which can equate to addition power, and can allow for a richer fuel mixture which also can equate to additional power.

Now if you are talking newer and contemporary autos and trucks, that is a whole nother ball game. Todays cars are engineered and designed to run efficiently at hotter temps and it also reduces emissions. But they also use a lot of aluminum which absorbs and dissipates engine heat. Cast iron holds heat. 

*My opinion* - I like and use the 160 T-stat just to keep engine temps down - almost in the range you shared which in my experience would be perfect numbers. Nice and cool going down the road, 180 in stop & go traffic without worry of boil over, cooler oil temps, and when I open the engine up I am not looking to listen if the engine is pinging because it is heat soaked. But, with any high performance engine/car, I don't baby it and burning rubber and wide open throttle blasts are my joys - so I want a cooling system that works and takes all the heat I put into the engine. :thumbsup:


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## geeteeohguy (Feb 2, 2008)

I'm with Jim. Been using nothing but 160 T-stats for 40 years in these cars. It's hot where I am, and I like my cars to run 180-220 as much as possible. Have never had a Pontiac that actually would run at 160 degrees.....and that's too cold anyway for thermal efficiency. You want the engine to run hot enough to be efficient and burn off condensation in the oil, and you want it cold enough so it does not ping.


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## Lemans guy (Oct 14, 2014)

Really you want to be like Elvis...cool!

I am with Pontiac Jim and geeteeohguy,..I run a 160 degree T-stat in my 461 stroker. An hour on the highway at 70 will give me about 185 degrees, around town stays at 160. I use a flowcooler WP as well and a tight impeller clearance.

As for AFR, I am real particular on that and run wide and O2 in each exhaust and a meter to read in both on dash. I run with the exhaust crossover open, keeps the intake hot for instant vaporization of the mixture, yet the engine is cool, but that is a whole mother discussion.

As far as condensation the oil temps are hot and water evaporates at various temperature not only boiling at 212 degrees. The water, in the form of sweat that evaporates off your arm is not boiling at 212,... yet there it evaporates. Clouds are water vapor and so is fog, none of those are at boiling temperature. But a good oil filter, I only use Wix and a good PCV system together will evacuate the water vapor and the blow by and crud. 

I was down at Butler Performance they had supplied and cut my short block, super crew, I asked one of the guys what thermostat they recommended. He said they put a 160 degree thermostat in every......every....engine they build. Now you should see some of those engines they have. I believe they no hot Empl can cause detonation and cooler running is better.

I also use an ME Wagner PCV valve and catch can to keep crankcase vapor, blowby and crud to a minimum. It pulls a vacumn of 1 to 3 HG 99% of the time,...you average cheap 5$ PCV valve maybe pulls vacumn 10 to 30% of the time. 

So if you are cool, my recommendation is to stay cool :nerd:and work your AFR with a good carb and an AFR meter on or off the car.:nerd:


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## pcguy (Jul 7, 2014)

The rating of the thermostat only determines when it opens -- the cooling system, ambient temps and engine load determine how hot the engine runs. At least that's how I understand it... :cheers


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## Lemans guy (Oct 14, 2014)

Totally agree, if you run a 195 thermostat and the car runs at 180.....it is either stuck open, or running so cool that it does not reach 195.

Often the heater core acts as a radiator because it is just a mini one, and with flowcooler WP and tight impellers and four row large tube radiators you can get em to run cool, you do't want detonation and pinging and when superheated cylinder walls and compression causes that mixture to detonate prematurely.

I have a snorkel air cleaner and it drops on each side of the carb inside of the engine. Colder air is denser and effects the mixture, I am not a believer that it gains more HP, certainly not on a street car, and not into running jams for outside air. I used that ainly for hood clearance, but I have checked the temos at the snorkel and usually about 10 or 15 degrees above ambient air...so if it is 80 degrees maybe 95 at snorkel......

once in my intake the exhaust crossover is open and it is real hot, vaporizes instantly, because hey it is only in there for micro seconds passing thru...so the mixture in the cylinder is already hot and vaporized, engine temp may be 170.......not a factor in AFR 

thermostats begain to open at rated temp and even can a bit earlier, as wax pellets are not that super exact.....once running down the road it is all the other stuff in your cooling system that determines your running temp.

By the way, we all talk constantly about the coolant temp, but take a temp gun or thermo gun and after a good run take it out and shoot it around your engine compartment, Carb temp? Fuel lines? both bowls? intake runners? air cleaner? exhaust manifolds? ........even the coil and alternator, see what you get.

if you check at the fender just inches away, you will see it is close to ambient......

If your is boiling from heat soak you may find the problem.................these temps are not coolant temps.....

:nerd::nerd::nerd:


if your fuel lines and carb are real hot...your gas may be boiling in the lines and bowls causing hard starts hot......the distaillation curve on summer blend gas is about 140 for E-10 and 170 for pure gas......if you are up in those ranges on carb and fuel lines might need some heat shielding!:nerd:


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## 69 237 (Feb 18, 2018)

That definitely make sense. Thank you all for the input. I'll try a 160F thermostat and see how things go.

I've always replaced the thermostat while draining coolant. Can you swap the thermostat without draining coolant?


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## Lemans guy (Oct 14, 2014)

Partly, but it just a mess and nobody does that.....if you are going to open it up...for a new thermostat put in fresh coolant.


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## PontiacJim (Dec 29, 2012)

69 237 said:


> That definitely make sense. Thank you all for the input. I'll try a 160F thermostat and see how things go.
> 
> I've always replaced the thermostat while draining coolant. Can you swap the thermostat without draining coolant?



I always suggest drilling a couple 1/8" holes in the outer ring of the T-stat. Just make sure you don't go too far out and drill into the gasket/seal area.

Why? Should the T-stat fail, the engine typically heats up quickly with no coolant circulating and then, because the T-stat is stuck closed, the coolant temp will rise fast as it reaches the boiling point of your mixture and then when it hits that point, the pressure forces it back out the lower radiator hose and the coolant violently blows out the radiator cap - at least my experience.

With the holes, the engine will still overheat, but if you catch it on the gauge, it'll give you a little notice as the temp will rise slower, rather then get to a point where the coolant boils and violently pukes out. The holes allow the pressure inside the block to escape through the holes, as small as they are, and not trap the pressure causing the fast rise in engine temps and the violent boil over experience. Gives you a little extra time to pull over and less chance of losing most of your coolant should you need to set to let the engine cool off and then make a dash to a safer or better place for the repair. 

You can test the opening rate of any T-stat in boiling water and use a thermometer to indicate the temp, but this does not mean the T-stat will not fail sometime down the road as it cycles open and closed. I personally feel that some brands use a poor grade of spring wire to open and close the T-stat and they heat fatigue until they just fail. I can't recommend any brand as even the good old brand names most of us are familiar with are sourced outside the country. Had a '97 Toyota that I put 3 into it with each failing several months into use. Finally just gutted the T-stat and used the brass ring to act as a flow regulator. Car ran cool and didn't throw a lot of heat in winter. In summer, it would heat up in stop/go traffic only because my electric radiator fan did not want to come on when engine temps got hot - so I would throw on the AC which activated the electric radiator fan which then operated constantly as part of the design when the AC was used. This would bring the coolant temps right back down to normal and even a little cooler. So I used the AC switch to activate my electric radiator fan because it was lazier than running a direct power source hooked to a toggle switch. LOL

So keep this in mind. I like to carry an extra T-stat, gasket, and gallon of coolant in the trunk on trips beyond city limits. I also swear by AAA when owning an older car as they will tow up to 100 miles (Gold Plan) free twice a year. Some insurance companies also offer this roadside feature at very little expense, but you have to ask for it. :thumbsup:


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## cij911 (Oct 25, 2017)

69 237 said:


> That definitely make sense. Thank you all for the input. I'll try a 160F thermostat and see how things go.
> 
> I've always replaced the thermostat while draining coolant. Can you swap the thermostat without draining coolant?


This makes no sense at all.....

If your car is NOW maxing at 180* after sitting and idling for a while, then your cooling system is adequate for your car and your 195* thermostat is stuck open.

I do NOT believe in installing 160* thermostats as this used to be a cheap way to fix another problem. A 160* thermostat will be fully open at 160* and you will likely experience little operating temperature to what you have today. If you want the car to run a tad warmer, then my strong recommendation would be to buy a 180* thermostat, which will open fully at 180*, and with your adequate calling setup you will likely run between 180 - 195*.

Good luck


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## 69 237 (Feb 18, 2018)

I've been running a 180F mr gasket thermostat for the last couple years now. I've only got higher temps up to 200-205F when extended idling in the dead of summer after extensive heat soaking. That makes me think my fan clutch may be getting tired. Ill replace that next and then try a 195F stat on the next go around as I think the 180F on cooler fall/spring days makes it take a bit longer to warm the carburetor and make it happy.


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## PontiacJim (Dec 29, 2012)

69 237 said:


> I've been running a 180F mr gasket thermostat for the last couple years now. I've only got higher temps up to 200-205F when extended idling in the dead of summer after extensive heat soaking. That makes me think my fan clutch may be getting tired. Ill replace that next and then try a 195F stat on the next go around as I think the 180F on cooler fall/spring days makes it take a bit longer to warm the carburetor and make it happy.


You temps are good under those conditions - 200-205. The intake manifold exhaust heat crossover should be what warms up the intake/carb. The 195 T-stat is also used because it does heat up the engine for those who experience cold climates. A 160 T-stat, or even 180 T-stat, would not throw enough heat out the heater in the dead of winter. The higher 195 T-stat is also linked to emissions - hotter engine burns the fuel more efficiently. A factory air cleaner with closed top and a snorkel inlet also can help as it draws in heated air from under the hood. The factory air cleaners also had the heat stove/pipe coming off the exhaust manifold going to the snorkel with a bi-metallic operated flap to regulate the heated air - maybe this when it gets colder?

All you can do is try it and see how it goes.


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