Engine Temp. - How hot is too hot - Chevelle Tech
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post #1 of 25 (permalink) Old Apr 12th, 19, 8:36 PM Thread Starter
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Engine Temp. - How hot is too hot

I plan to do hot rod power tour this summer with my 66 396 325hp essentially stock engine and fully expect to be in lots of stop and go traffic that will thoroughly test my cooling system. One measure that I've taken is switching over to Evans Waterless coolant. It is my understanding that the theory is that the coolant will not boil thus eliminating the hot spots. This will allow the coolant to continually absorb the heat at all locations by staying in contact with the metal engine components.
My question is how hot can the coolant/engine get if the hot spots are eliminated? Can you safely run the engine if the coolant is at 240-250 degrees as long as there are not concentrated areas of hot spots?

I hope I've explained this so you can understand what I'm thinking.

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post #2 of 25 (permalink) Old Apr 12th, 19, 9:02 PM
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Re: Engine Temp. - How hot is too hot

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Originally Posted by berg1954 View Post
I plan to do hot rod power tour this summer with my 66 396 325hp essentially stock engine and fully expect to be in lots of stop and go traffic that will thoroughly test my cooling system
Mark

Mark,
My 71 was my daily driver for three years when it was new. Plenty of stop and go traffic along with many a trip from Maryland to Boston. I never had a problem with over heating.


Your 66 was probably somebody's daily driver when it was new also. Why should it be any different now ???? As long as the cooling system is in decent shape you shouldn't have anything to worry about.



As far as temperature goes I would not want to see it any more than the original design. Probably 180 for that car. 200 might not hurt anything for short periods but no way I would want to see 240-250 Engine parts will expand, clearances will change etc etc I dont care if you have hot spots or not.



Personally I would put good old green coolant in it and stop worrying.
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post #3 of 25 (permalink) Old Apr 12th, 19, 9:26 PM
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Re: Engine Temp. - How hot is too hot

How hot is too hot is a good question.

Setting aside the questions about the waterless coolant, older engines tend to run well at the 180-190 range, but there are draw backs. At 200 degrees, you get the least amount of cylinder wall wear, the best economy, and the best emissions provided the engine is well designed which, sadly, engines from the '60s lack the same degree of engineering development we have on today's engines.

That's why cars like the later 5.0s run at 200 degrees, and even though you can run them cooler, it really isn't the best idea.

If you're having trouble with overheating problems now, I would definitely repair your cooling system before heading out on the open road. If a properly functioning cooling system (that is, every component is working correctly) isn't sufficient to cool your engine because, let's face it, lots of cars got spit out of the factories with subpar cooling systems during the '60s then you can look at adding a larger radiator, a higher flow thermostat (not merely a cooler opening thermostat), a higher pressure radiator cap, and possibly a higher flow water pump. That last one, you need to be careful though, because you can blow your cooling system if it isn't up to handling the pressure produced by the high performance pump.

Just some thoughts. And I would just consider those ideas to be starting points definitely research anything I've mentioned.
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post #4 of 25 (permalink) Old Apr 12th, 19, 11:46 PM
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Re: Engine Temp. - How hot is too hot

I have two 70s, A one owner LS-5/M-22 with C-60. Cooling is 100% stock, Down to the rubber/Stainless trim on the fenders near the windshield.
My driver is a 70 Nomad Wgn. with a 468 and a 700R4 and factory C-60 Converted to R134. Sitting in traffic on a hot day in the 90s with the A/C running the 468 will hit 215 at times.
Both of my 70s have the stock VO-1 cooling systems ( with ALL the details the factory installed) I run nothing special in the stock 4 row Copper Brass Rads. in both 70s. Green anti freeze from Advance auto and water from my garden hose.
A lot of cooling issue are Self Inflicted over the years with little changes here and there. I would start with a REAL FINE engine tune, Get the engine bay equipped as it left the factory. This may get you to " Square One ".
For over 50 years I have used nothing special to keep the engines KOOL. Spigot water and Green A-Freeze. On my driver 70 LOOK Between the core support and the 4 row rad. You will see a space about 5/8
" to 3/4" GAP, I got some sticky back, black foam tape and closed this GAP.
Just get back to basics! You are NOT going to buy some magic LIQUID that is going to help. A lot of overheating issue are Missing parts under the hood. Chevrolet was not doing car buyers a favor when the installed Rubber seals, Splash guards, along with other items. If you do not have the factory style " DUCT WORK " under you hood with everything in place, This may cause problems???????
My one owner LS-5/ 4 speed did not get hot in 1970, It does not get hot today, ALL the factory parts & pieces are in place.
Just a little bit at a time and you will get it KOOL. A lot of folks on T-Chevelle are here to help. Just keep asking questions.
Bob

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post #5 of 25 (permalink) Old Apr 13th, 19, 8:41 AM
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Re: Engine Temp. - How hot is too hot

50% coolant and water will not boil until something like 265 degrees with a 15 psi pressure cap.
I would not address overheating with coolant change, with a good pressure/return cap, and overflow return system, (I know, I know...) a car will not boil over until it is WAY overheated.
As for actual temps, I would be concerned with over 220 and still climbing.
With overheating, the real damage is what it does to your oil, not the metal parts.

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post #6 of 25 (permalink) Old Apr 13th, 19, 8:57 AM
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Re: Engine Temp. - How hot is too hot

The problem with the early Chevelles is the radiator can be too small. You can make them work, yes, but still won't cool like a later Chevelle. You will notice that in 1968 and later the Chevelle radiator grew about 40% in surface area (from 380-400 sq in to like 540 sq inches - that's a big jump). My guess is that they figured out there was a problem when you got the AC involved and they did a redesign. They also redesigned the front for more engine to radiator fan clearance to account for the enormous fan shroud and I think they also went with a bigger fan too. I have noticed on this site on over heating 9 times out of 10 it is a 1964-1967 Chevelle (assuming everything is done right). You almost never hear about the later Chevelles overheating (assuming everything working correctly). If a later Chevelle does run into an issue they have lots of real estate to run really big fans etc. The question is do you have AC? If you don't that will help. Just make sure you got a good size and cleaned out radiator with a good fan set up as described above with a shroud. Once the car is moving 30-40 mph you should be OK. AC is the issue that I think puts a stress on the system and can raise temp 20+ degrees at a stop light. Work with what you have before you go the other route your not pushing the envelope here so you should be able to get a good solution. You want temps to be less than 220 on a very hot day and like 190-200 on a normal day (if you can keep them 200 and under all the time great). Once it gets up there - there is an issue and it is tough to get temps down unless the car is moving. Temperature creep is not a good thing if it just keep creeping up and up.
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Last edited by Lew540; Apr 13th, 19 at 9:01 AM. Reason: adding stuff
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post #7 of 25 (permalink) Old Apr 13th, 19, 9:20 AM Thread Starter
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Re: Engine Temp. - How hot is too hot

Thanks for all the responses. Well it looks like the consensus is that if the cooling system is up to the factory spec and using the standard green fluid I should be all set. I have gone through the cooling system, the radiator (4 core copper) has been flushed and pressure tested, shroud installed with the bottom gap between the radiator and shroud sealed with foam, 7 blade clutch fan, high flow water pump. The vacuum advanced it connected to manifold vacuum for cooler running at idle. I also installed a classic auto air system during the restoration so I will have the additional heat from the AC. (Got to keep the other half happy)
I am trying to do all I can to avoid overheating, sort of takes the fun away sitting on the side of the road. I have already installed the Evans so I'll go with that and see what happens.
Just trying to determine when to shut it down if it does start heating up in traffic. As Ed mentioned, I hadn't thought about what the heat would do to the oil. As suggested above probably 220 would be the limit.

Thanks again for the opinions
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post #8 of 25 (permalink) Old Apr 13th, 19, 9:36 AM
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Re: Engine Temp. - How hot is too hot

From having an older turbo car at one point, I learned that oil is engineered to run at around 200, its where it has its best properties, where it designed to run. Synthetic can stretch higher/lower from that nominal point. So coolant temps should be regulated to near that level.

I use a oem style steup with clutch fan and so far so good. green jiuce. Once used a can of "cooler", like a water wetter whch also knocks temps down.

Been lucky so far, but did lose a water pump and found that the cap didnt let loose like it should have. I borrowed a pressure tester thingy to check the next one to be double sure. It was a mid priced good reproduction from our resto local vendor. ( $27-30). And while I did a compression test afterward and found no issue, a steam port gave way soon thereafter, requiring a head gasket swap. " pressure check your caps gentlemen!"

I only hope your high flow pump doenst flow too much! You should be good to go! I'd test before I went "on mission" to be sure.

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post #9 of 25 (permalink) Old Apr 13th, 19, 11:07 AM
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Re: Engine Temp. - How hot is too hot

Quote:
Originally Posted by 427L88 View Post
From having an older turbo car at one point, I learned that oil is engineered to run at around 200, its where it has its best properties, where it designed to run. Synthetic can stretch higher/lower from that nominal point. So coolant temps should be regulated to near that level...
Not true engine oil needs to reach at least 220 to get rid of moisture and deposits. Do not confuse coolant temp with oil temp. The operating temp range of oil needs to be 230-260.

On a side note, ethyl glycol antifreeze has a minimal effect on high temperatures, it was designed to prevent freezing. Pressure is the key to keeping an engine from boiling over.
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post #10 of 25 (permalink) Old Apr 13th, 19, 11:20 AM
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Re: Engine Temp. - How hot is too hot

Mount a 16" spal, wire it up using their on/200 off at 185 switch, keep your manual fan. Worry free

Dont like just having 1 fan if it goes out youre stuck....plus the temp fluctuation. Used to it staying steady

On running temps with todays ethanol keep it running cool as you can so you dont have percolation/hot restart issues
Mine will idle all day (with 82 deg overlap!) when it creeps up towards 200 it drops down and gets lazy.

Quote:
This post is a duplicate of a post that you have posted in the last five minutes.
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post #11 of 25 (permalink) Old Apr 14th, 19, 6:19 AM
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Re: Engine Temp. - How hot is too hot

You should only add enough ethylene glycol to prevent your coolant from freezing in your area. The more EG you add, the worse the transfer of engine heat to the coolant is. That is why EG is recommended in percentage values so that you have enough to prevent freezing, but no more.
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post #12 of 25 (permalink) Old Apr 14th, 19, 7:32 AM
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Re: Engine Temp. - How hot is too hot

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Originally Posted by Gtogeoff View Post
You should only add enough ethylene glycol to prevent your coolant from freezing in your area. The more EG you add, the worse the transfer of engine heat to the coolant is. That is why EG is recommended in percentage values so that you have enough to prevent freezing, but no more.
Yes, but no, increased EG also raises the boiling point, so if you are running hot, you won't casue over pressure as fast and lose coolant.

FWIW, I had a cooling problem, I had a huge stock type rad with clutch fan, no shroud. I swapped to a generic parts store aluminum core plastic tank, and a homemade/hacked up Silverado shroud and no issues. The amount of airflow through the new rad is amazing. Partly due to the shroud, and also I think the old huge copper one just didn't flow air well, plus corrosion inside didn't transfer heat from the coolant to the metal as well.
I have an anemometer (wind gauge) and I did measure airflow at idle, I forget the numbers but it was a HUGE improvement.

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post #13 of 25 (permalink) Old Apr 14th, 19, 9:04 AM
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Re: Engine Temp. - How hot is too hot

Guys,

Simply:
At 0 psig:
Water boils at 212 F
50/50 coolant boils at 226 F

For every psi increase in cooling system pressure, you get an increase in boiling point of about 3F. For a typical 15 psi cap, you're looking at a maximum psi of 226 + 45 = 271 F boiling point.

I say maximum because the stars must align for you to actually reach these pressures in normal operation. In other words, if you have leaks, if you did not purge the air properly, etc., you will not reach the maximum pressure until the system is boiling over. Remember, your water pump only makes flow, the increase in pressure occurs due to the coolant thermally expanding.

Anyhow, the increase in pressure is key to keep the coolant from boiling (turning to steam) inside the engine. If the coolant boils at the hot spots inside the engine, you are making air bubbles...air bubbles which do not cool and you are losing base material (metal) in the engine due to cavitation erosion as the bubbles implode. If you want to see how the steam bubbles form, boil water on the stove and watch the boiling process in action an note how the bubbles slow the boiling process due to insulation. We must keep the bubbles away with proper care.

Tips:
Don't use tap hard tap water - public water is "hard" water. Well water can be "hard" water. Use either deionized or distilled water. Corrosion promotes leaks. Use a reputable coolant, and do not mix coolant types.

Water transfers heat better than coolant - never use 100% coolant (concentrated), always ensure 50/50 mixture unless you are running below -34 F. You can cause engine damage by using 100% concentrated coolant.

Remove (bleed) the air from the highest point in the cooling system. If there isn't a place to bleed the air at the highest point, tilt the car or install an air bleed - you will thank yourself later.

If you are overheating at idle, you generally lack air flow.

If you overheat above 40-50 mph, you generally lack coolant flow or your "system" has major issues. System could include engine, timing, leaking head gaskets, etc.

Fan shrouds are vital, as are air dams under the radiator support. Fans work by creating low pressure between the fan and the radiator. You need higher pressure on the other side - air dams help get this done while you are moving. By nature, air on the engine side of the fan "high" pressure, particularly if it cannot escape the engine compartment fast enough.

Another thing to consider is to "ensure only cool outside air can be pulled through the radiator." Generally factories do a good job with the shroud, is this true on your car today? If you are using electric fans, how are you keeping hot engine compartment air from re-entering the radiator at the top and sides? When you are stopped, the high pressure in the engine compartment will escape to low pressure areas...right in front of your radiator if it is not sealed off. Seal it off!

Generally, the closer you stay to factory cooling specifications, the less trouble you will have as the small details are already well handled.
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post #14 of 25 (permalink) Old Apr 14th, 19, 10:21 AM Thread Starter
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Re: Engine Temp. - How hot is too hot

Lots of good cooling system information shared. It's important that the cooling system is in good shape and that the system can contain the pressure along with the proper mix of coolant. The key is to prevent the coolant from boiling. That is the reason I decided to switch over to the Evans waterless coolant. It's boiling point is 375 degrees which will help prevent localized boiling at the hottest locations and it won't build pressure from coolant expansion.

So when an engine overheats what damage occurs. I believe head gaskets, warp heads are typical. I would think that the damage was caused by extremely high temperature of the metal component due to loss of cooling from the coolant boiling inside the water passage opposite the heat source. If the coolant boiling is eliminated can one of our older engines operate at a higher temperature?

If so, than how hot? As mentioned in an earlier response, oil temperature may become more of a factor. Does anyone know if there is any correlation between water and oil temperature?

Bottom line, if necessary can I push my older engine to a higher coolant temperature since there shouldn't be any hot spots when using the Evans coolant. I certainly want to shut it down before any damage can occur since I'll be a long way from my garage.

Thanks again
Mark

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post #15 of 25 (permalink) Old Apr 14th, 19, 4:36 PM
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Re: Engine Temp. - How hot is too hot

OP, I drove my 66 4speed 325hp Chevelle for a lot of years with nothing but the "Idiot" light on the dash. When I finally had the chance to install gauges, I found the car ran right at the 180* that the "Factory Thermostat" was. I never did anything special, 50/50 water/antifreeze. Factory 4 blade fan, "No Shroud". Even now with over 100,000 not running its best, with a replacement radiator, it still runs at 180*. You can watch the thermostat open and close on the gauge. I hope this helps.

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