Railguy

On my way back from OC I noticed my temp was about 170.When I hit the internet states I doubt if made to 185. This was in the rain and kinda cool . When it gets hot this summer I'm sure it will be above 185 . I can't remember what thermostat I have. But is 170 to cool? It was 170 for over 100 miles. I Thought finding a piece of cardboard to bloke it off.
Railguy

hookem horns

You should never have to do this with a properly operating thermostat. Well maybe if outside temps are below -0-. I would take out the thermostat to see what temp range it is, if it is stuck open, or even removed by a prior owner. You can also test it in a pan of water on the stove and a thermometer to see where it really opens but new ones are not expensive. Your temp gauge could be reading low too. I think factory thermostat was 190 and lots of folks here recommend 180.

steverw

I have always used 180 degree Tstats. I also was always told 180 is the correct temp for these old cars to run, however there is absolutly nothing wrong with 170. My 65 Vette has a 180 stat and most of the time stays straight up and down on 180, however i always felt it ran alittle better at around 160-165.

oldcutlass

I'll be willing to guess you have a 160 degree thermostat in there. 170 should not hurt the engine or trans. If you had a 180 in there, the temp would of been around 185-190. I'd just monitor it, you should be fine. Just remember a thermostat maintains the minimum temp the engine will run, the cooling system maintains the maximum.

Oldracerjones

I was talking to a cooling specialist at a local garage the other day when I have my radiator cleaned up and tested. He said for a warmer climate (like here in Texas) you need at least the 180 but he prefers the 190 since the thermostat keeps the water in the radiator longer for maximum cooling.

Fun71

Oh no, not this again. We have had multiple discussions about this, with lots of information on the thermodynamics of cooling systems and such; bottom line is the above statement is incorrect.

Railguy

I thought I had a 185 in it with a 1/8 hole drilled in it but now I'm not sure. My concern was that it may not be up to temp enough to run properly. I'm not worried this summer it should be higher. If not then start looking. Driving in the rain and the temp in the low 70 s could explain the low engine temp. Maybe I should pull a plug and check on the fuel mixture.
Railguy

Oldracerjones

It's people like you that make this site difficult. If all of us had your superior knowledge and have been on the site for 30 years maybe we will be as smart as you someday. I will tell the mechanic that told me this that you, the thermodynamic engineer, have decreed he is wrong.

oldcutlass

Oldracer, think about how a thermostat works... It controls the minimum operating temp of the engine. Its there to block the water flow until the water temp reaches the listed temp on thermostat. At that point it starts to open and the cooling system maintains the maximum operating temp. How does the thermostat once open keep the water in the radiator longer?

Railguy

All I can say is WOW.
Railguy

Railguy

Well it's a 180 degree thermostat. So I guess it's either the thermostat or the temperature gauge.
I also went from 272 to 343 gears. So I guess the fan and water pump are turning faster I don't think that would effect it but thought I should mention it. Also changed the oil. Went down one size on the jets too. I took the same trip last year temp was right where should be around 185-to 190. Never verying more then a couple of degrees. It was cooler last year but no rain. I m going to put the thermostat in a pan of water and see where it opens.
Railguy

Railguy

It started opening around 147 - 148 so I think that's the problem. They had a couple kinds of thermostats at the auto zone. One was a racing thermostat. I ask what the difference was he said the racing one once it opens it stays opened where as the others open and close to maintain a temp. I never heard of this. Is that right?

oldcutlass

I like the Stant Superstats. Run a 180 degree and you should be good to go. Me thinks the auto parts guy has no clue.

Railguy

The one I took out was a stant 180 from summit . As far as the guy from auto zone goes doesn't surprise me.
Railguy

therobski

Guys this subject has been worn out on this site. I will say this, my opinion: "cooler is better" The high performance 455 build in the 67 pictured wears a lot of aluminum aftermarket goodies (dissipates heat quickly) suburban radiator, shroud. Either way stock or not a cooler engine runs better-less chance of hearing a ping, you can advance the timing for better performance, hard starting problems after sitting in a bit before restarting, the list goes on. This 455 in Dallas summers runs 160-180 sitting at a light. On the road stays 160-170, in the fall-winter 150 -160 that's it and use 10-30 oil. It pull your shirt off on a launch from a light. Will not run it hard until the oil gets good and warm, probably opened a can of worms!!

m371961

I agree with Robski. The only downside to running cooler is getting enough heat in the winter.
The cooling specialist that says a 190 stat keeps coolant in the radiator longer allowing the engine to run cooler is flat out mistaken. Once it opens as much coolant flows no matter what thermo is there.
On Hi-Po engines in the 60s and 70s, we always ran 165 thermos and wore more clothes and waited longer for warm up or used cardboard in the winter. If you got stuck in traffic on a hot day and your engine is at 175 or 180 you have more room and time for a rise in temp then with a higher thermo.
I remember when 190s appeared, I was stunned until I learned it was a emission thing.
The parts guy may have been talking about thermos that when failed stay open, not closed. I have heard of these, but know nothing about them.

therobski

Yes sir m371961, here in Dallas I need A/C over heat-so I guess part of this depends on where you live and how old you are!!!. The 67 has no heat or A/C its waiting for a new A?C system. I removed all the factory A/C and heater components. I took this car and broke the 455 in on the 2008 Power Tour and went almost the distance. I will never go 2500 miles in an old car without A/C again.-Age !! been there done that

Railguy

The 190 thermostat makes no sense . Sure it stays in radiator longer but the coolant in the engine is hotter when it goes into the radiator . A cooler thermostat the coolant would not be in the radiator as long but would be cooler when entering the radiator.
In 60s and 70s gasoline was a lot different .
I don't know what temp is best that's why I am asking.
Railguy

m371961

Interesting thought about the fuel of today and if it makes a difference regarding the best temps in old high comp. carb engines. I would THINK, that with lower octane fuel one would want a lower temp to reduce pre-ignition and pinging troubles. Maybe a lower temp is less efficient, but it shouldn't do any harm.
I would be open to hearing other opinions.

Railguy

Mileage before new thermostat 12 mpg 204 miles on interstates non stop. After new thermostat 13+ .4 trips 55 miles each mostly interstates. I think the engine wasn't up to operating temperature. And it's running around 185 and warms up mu have faster.
Railguy

Lewbo

I have a water temperature gauge in my 1962 cutlass. And It shot up up to 220 when I changed the valley pan intake gasket. The temperature stayed around 180 before the change. The reason for the change was seepage of antifreeze at the rear of the intake. My problem came about because I didn't use the proper torque sequence on the in take bolts. Re torqued to specs and problem solved. I still use my factory fan and radiator. I posted this because Its something else you may want to check before building a shroud or replacing the fan.