66 327/350 What is Normal Operating Temp

[Cathy S.]

It was 97 degrees today and at stop lights the temp got up to 210 with the a/c on. It did drop down when moving. Got me thinking what is the safe ranges?

[Joe L.]

Re: 66 327/350 What is Normal Operating Temp

It was 97 degrees today and at stop lights the temp got up to 210 with the a/c on. It did drop down when moving. Got me thinking what is the safe ranges?

Cathy------

If you're maintaining 210 under the conditions you describe, I'd say you're doing very well. If you were doing extended idling under the conditions you describe, I think you might see the temps get to 220, or so. I don't like to see it go much higher than this. However, if you have a 50/50 coolant mixture and you're cooling system pressure cap is maintaining pressure at 13 or 15 PSI, you could probably go higher without hurting anything.

Assuming that your gauge and sending unit are indicating accurately, you don't want the temperature gauge to get into the red zone.

[Michael A.]

Re: 66 327/350 What is Normal Operating Temp

Cathy------

....Assuming that your gauge and sending unit are indicating accurately, you don't want the temperature gauge to get into the red zone.

Cathy
Joe's last line is pretty important. The fact is that most dash gauges in old Corvette's are not very accurate. You may want to invest in a small infrared thermometer. If you get the engine good an warm (eg. 210F) you can stop the car, open the hood and point the IR thermometer to at the thermostat housing, you can get a reading that should be comparable to what you read on your dash gauge.

On my car I found my dash gauge reads about 30F higher than the IR. It's consistently in that range so I use the dash gauge as a very gross indication. When I go on trips I make sure I have the IR in the glove box and check the temp when I stop for gas, etc. It's a good peace of mind.

You might wonder why I don't just fix the gauge? Fair question. Check the archives and you'll read a lot about temperature senders and gauges and the challenges of getting them to read correctly. Until such time that I do a restoration I will just keep my IR thermometer handy.

Have fun, keep driving and STW!!!!

[Cathy S.]

Re: 66 327/350 What is Normal Operating Temp

Thanks guys! I put an IR gun on the car today and the gauge is pretty accurate. It was 95 today and running in traffic w/air and extended idling it got to 212. I'll seal the fan schroud and see if it cool.

[Duke W.]

Re: 66 327/350 What is Normal Operating Temp

With a 15 psi cap and a 50/50 mix of glycol/water, the boiling temperature is 265F.

Given the conditions you reported, I don't think you have a problem.

Some modern cars with electric fan(s) only don't even turn them on until 230F based on engine temperature only, but AC demand will probably turn them on sooner in low speed traffic.

In fact, some modern cars will actually run cooler in traffic with the AC on than off because the cooling demand for the AC system is more than the engine, but the engine temp also benefits from the fan air flow.

As far as normal range is concerned, if the engine has a 180 degree thermostat I consider it to be 180-230 with the high end of the range being "normal" in extreme conditions such as extended idling (with or without AC on, if equipped) in 100+ degree ambient temperatures.

Some think the engine should run all the time at the thermostat temperature. This is an incorrect perception. The thermostat merely establishes the minimum operating temperature. The upper end is based upon some margin from the coolant's boiling point and 230 still give you 35 degrees margin.

Particularly on small blocks the aluminum radiator and clutch fan represent the best technology of the era and there is really no better cooling technology, today, so under most conditions, especially when the car is moving, small blocks will run at thermostat temperature because there is lots of cooling system capacity/margin.

Big blocks generate more heat and have little more cooling capacity, so they will tend to run hotter than SBs in the same conditions.

Duke

[Joe L.]

Re: 66 327/350 What is Normal Operating Temp

With a 15 psi cap and a 50/50 mix of glycol/water, the boiling temperature is 265F.

Given the conditions you reported, I don't think you have a problem.

Some modern cars with electric fan(s) only don't even turn them on until 230F based on engine temperature only, but AC demand will probably turn them on sooner in low speed traffic.

In fact, some modern cars will actually run cooler in traffic with the AC on than off because the cooling demand for the AC system is more than the engine, but the engine temp also benefits from the fan air flow.

As far as normal range is concerned, if the engine has a 180 degree thermostat I consider it to be 180-230 with the high end of the range being "normal" in extreme conditions such as extended idling (with or without AC on, if equipped) in 100+ degree ambient temperatures.

Some think the engine should run all the time at the thermostat temperature. This is an incorrect perception. The thermostat merely establishes the minimum operating temperature. The upper end is based upon some margin from the coolant's boiling point and 230 still give you 35 degrees margin.

Particularly on small blocks the aluminum radiator and clutch fan represent the best technology of the era and there is really no better cooling technology, today, so under most conditions, especially when the car is moving, small blocks will run at thermostat temperature because there is lots of cooling system capacity/margin.

Big blocks generate more heat and have little more cooling capacity, so they will tend to run hotter than SBs in the same conditions.

Duke

Duke-----


As C4 specialist Gordon Killebrew always says, if your car starts to overheat, don't turn the air conditioner off, turn it on!

[Stephen B.]

Re: 66 327/350 What is Normal Operating Temp

If you feel everything in your system is operating properly, but would like the temperature to drop 20 degrees try a bottle of Red Line brand water wetter.This product is compatible with anti freeze and aluminum radiators. I have used this product to solve overheating problems on big blocks on 90+ degree days.I'm sure it will help you. It's about $6.95 at Auto Zone, or Jegs.
Good Luck
Stephen Barrett (21558)

[Duke W.]

Re: 66 327/350 What is Normal Operating Temp

Most people who have used that stuff admit it does nothing.

It's designed for race cars where the rules don't allow antifreeze.

There is no guarantee that it is compatible with all antifreeze corrosion inhibitor packages.

A 50/50 blend of distilled water and Zerez G-05 is the best coolant for vintage Corvettes to protect against freezing, boilover, and, most importantly, CORROSION.

If the temperature consistently gets over 230 in hot weather, there is something wrong with the cooling system components, - inoperative fan clutch, clogged up radiator, and often a dead or improper vacuum advance that retards the total idle timing and throws excess heat into the cooling system.

The way to cure overheating is to find and correct the root cause of the problem - not add snake oil to the coolant.

In this case - 97 degrees outside, AC on, stop and go driving - 210F is perfectly normal and acceptable.

Duke

[Cathy S.]

Re: 66 327/350 What is Normal Operating Temp

Thanks all!

[Stephen B.]

Re: 66 327/350 What is Normal Operating Temp

As usually is the case Duke has replied with some good info and some not so good.First let me stress that Water Wetter is not a band aid approch to getting your operating temp. down.Everything in the system should be operating properly before introducing this product. thats were I agree with the Dukester.Were I disagree is with his claim that this product is incompatible with a 50/50 mix. It is in fact the only product of its kind that is compatible with antifreeze. The Dukester is thinking of a product called 40 below which was designed to be used in race cars that run straight water.I have used Water Wetter in several cars and recamended it to many folks with marginally hot running cars. It works very well in big blocks that like to over heat when the temp. outside is in the 90s and they are forced to idle in traffic. I would definatly not discribe it as SNAKE OIL Dukester. I believe thats a product for treating leather,which I would never put in a cooling system.

[Dick W.]

Re: 66 327/350 What is Normal Operating Temp

I agree with Duke on the Water Wetter type products. Marketing gimicks. I owned a radiator shop in another life and had customers tell me they had tried this product and that product trying to get their vehicle to run cooler. Quite often they spent more on snake oil products that it would have cost to have their radiators cleaned out.

[Clem Z.]

Re: 66 327/350 What is Normal Operating Temp

if it is a brass/copper type rad the fins loose contact with the tubes and there goes your cooling. the only fix is a re core job.

[Duke W.]

Re: 66 327/350 What is Normal Operating Temp

As usually is the case Duke has replied with some good info and some not so good.First let me stress that Water Wetter is not a band aid approch to getting your operating temp. down.Everything in the system should be operating properly before introducing this product. thats were I agree with the Dukester.Were I disagree is with his claim that this product is incompatible with a 50/50 mix. It is in fact the only product of its kind that is compatible with antifreeze. The Dukester is thinking of a product called 40 below which was designed to be used in race cars that run straight water.I have used Water Wetter in several cars and recamended it to many folks with marginally hot running cars. It works very well in big blocks that like to over heat when the temp. outside is in the 90s and they are forced to idle in traffic. I would definatly not discribe it as SNAKE OIL Dukester. I believe thats a product for treating leather,which I would never put in a cooling system.

"Antifreeze" comes in several different flavors. Notwithstanding those that are not ethylene glycol based, they consist of ethylene glycol and a carefully developed and tested corrosion inhibitor package. The three basic types are IAT (which is obsolete), OAT, and HOAT, all of which have been discussed many times in the past.

A mixture of pure water and the proper type of antifreeze for the types of materials in the cooling system results in a very carefully balanced concentration of various chemicals to provide maximum corrosion protection. The reason to use distilled rather than tap water is to not introduce any undesireable chemicals/ions that could degrade the corrosion inhibitors. Tap water has various salts along with chorine and fluorine, both of which are detrimental.

I've never been able to determine the chemical analysis of Water Wetter (or any other cooling system supplemental additive), so I have no idea if it is compatible or not with the various antifreeze technologies, which is why I recommend avoiding it, unless you have a race car where the rules say no antifreeze because it's difficult to clean up track spills.

The OEMs didn't use any supplemental cooling system additives (other than a couple of Bar's Leaks tablets) when our cars were built, and they don't use them on new cars.

If a vintage Corvette overheats or has chronically high operating temperatures in mild weather, find and fix the root cause of the problem.

Duke

[Stephen B.]

Re: 66 327/350 What is Normal Operating Temp

I agree with Duke on the Water Wetter type products. Marketing gimicks. I owned a radiator shop in another life and had customers tell me they had tried this product and that product trying to get their vehicle to run cooler. Quite often they spent more on snake oil products that it would have cost to have their radiators cleaned out.

Dick
With all due respect to your credentials and great experiance,Red Line Water Wetter works. Simply because you and Duke don't like any solution that isn't yours alone doesn't make it so.I will stress one more time that I would never advise someone to use Red Line Water Wetter unless they had a system already in perfect shape. Having said that I will also stress that cooling systems respond differantly to 90+ degree days than they do in 60 to 70 degree weather.If you ran a radiator shop you already know that.Let's also no try to confuse the issue by calling it this product and that product. I am endorsing only one product,made by Red Line because I along with many others in my area have succesfully used it.I would also never recommend anthing on this forum I hadn't used myself.Remember there's always more than one way to skin a cat,and your never too old to learn something new.Of course sometimes you can't teach an old dog a new trick.
Respectfully
Stephen Barrett (21558)

[Dick W.]

Re: 66 327/350 What is Normal Operating Temp

Dick
With all due respect to your credentials and great experiance,Red Line Water Wetter works. Simply because you and Duke don't like any solution that isn't yours alone doesn't make it so.I will stress one more time that I would never advise someone to use Red Line Water Wetter unless they had a system already in perfect shape. Having said that I will also stress that cooling systems respond differantly to 90+ degree days than they do in 60 to 70 degree weather.If you ran a radiator shop you already know that.Let's also no try to confuse the issue by calling it this product and that product. I am endorsing only one product,made by Red Line because I along with many others in my area have succesfully used it.I would also never recommend anthing on this forum I hadn't used myself.Remember there's always more than one way to skin a cat,and your never too old to learn something new.Of course sometimes you can't teach an old dog a new trick.
Respectfully
Stephen Barrett (21558)

Each to his own snake oil