How hot is too hot for the engine? (1969 350) - Team Camaro Tech
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post #1 of 16 (permalink) Old Jun 23rd, 17, 04:13 PM Thread Starter
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Danny
 
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How hot is too hot for the engine? (1969 350)

So I live in AZ and if anyone knows it gets hot here, this past Tuesday I believe it hit 119. Anyways its starting to cool down (110) and I was wondering how hot is too hot for the engine? Its a stock radiator and clutch fan. I obviously need the AC on which I know heats the engine up more then when its off. When driving around I get close to 220. Whenever it starts getting close to that I head back home in fear of overheating. Is 220 a good limit or can it get a little bit past that?
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post #2 of 16 (permalink) Old Jun 23rd, 17, 05:02 PM
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Your high temp is not a problem as long as cooling system retains its pressure as established by the radiator cap.
The higher the pressure, the higher the boiling point of the coolant.
Also, clean engine oil helps cool the internals, aka, the short block, as coolant cools the heads.
Heat does break down oil.
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post #3 of 16 (permalink) Old Jun 23rd, 17, 05:35 PM
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Re: How hot is too hot for the engine? (1969 350)

Nothing wrong with 220 on a 110 degree day with a/c on. I don't start getting nervous until 230.

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post #4 of 16 (permalink) Old Jun 23rd, 17, 06:32 PM Thread Starter
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Re: How hot is too hot for the engine? (1969 350)

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Originally Posted by 1968RallySport View Post
Nothing wrong with 220 on a 110 degree day with a/c on. I don't start getting nervous until 230.
Just drove about 15-20ish miles with about 70% being highway and 30% city driving and the gauge stayed just under 220 the whole time. Every time I started seeing it creep up to 220 before I'd turn back and not risk it but it seems to stay just under 220 even after being hot. So I think this answered my question but in mind mind, being any bit higher then directly middle in the gauge was sketchy to me.
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post #5 of 16 (permalink) Old Jun 24th, 17, 07:00 AM
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Re: How hot is too hot for the engine? (1969 350)

Where you live shouldn't really matter. I'm in Florida myself and we're already getting 100 degree days as well. 220 plus would make me nervous. I was hitting 210 and made some changes to get back to 185-190. Now, I don't have a/c, so not sure how much that adds to the operating temp, but I would imagine that under 200 would be achievable.

Have you always been running these temps or is it something new?

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post #6 of 16 (permalink) Old Jun 24th, 17, 07:27 AM
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Re: How hot is too hot for the engine? (1969 350)

Your cooling system is in place and adjusted to protect your motor oil. From thermodynamics the colder the heat sink and the higher the combustion chamber temperature the more work is available to be extracted. Get it too cold and your oil becomes grease which will not keep the bearing off of the crank, too hot and the oil oxidizes breaking down to ash which will grind your crank and other moving parts like sand paper.

Oil breaks down above 240 degrees, and unless you are running 5W40 it will not protect your bearings in places like Alaska were it gets nippy at night during the winter. Water boils at 212 degrees at sea level but if you live in Denver it boils far below that point.

You have a radiator pressure cap with a spring (that gets old and sags like all springs do with age) inside to increase the vapor pressure well above sea level to raise the boiling point of your coolant.

Your copper brass radiator AND HEATER CORE are soldered together which is weak compared to welding base metal. A welded aluminum radiator is much stronger so you can raise the pressure in the cap to 24 pounds instead of the stock 16 pounds without worry of blowing off a hose or splitting your radiator apart. This combination allows for a higher operating temp above the point at which your oil begins to oxidize. In a race car no worry as you are going to change it at the end of the race, but a real problem for a street car. Race cars do not have heater cores to worry about.

If you change your oil viscosity and keep it below 240 you can run your car at a cooler temperature. This is accomplished by installing a larger radiator and forcing air through it. Fan is used to cool the car below 35 mph, above that speed air pressure built up in front of our brick shaped cars will push air through the radiator if you restrict the air flow so that it can not go around it.

The shape of the car restricts the size of the radiator, in terms of height, Width is restricted by battery and head lights (though a wider radiator was used on higher horse motors in the Camaro), that leaves the thickness to be the most frequently changed variable. A bigger radiator offers more surface area to exchange the heat of combustion with the heat sink (atmosphere).

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post #7 of 16 (permalink) Old Jun 24th, 17, 07:59 AM
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Re: How hot is too hot for the engine? (1969 350)

There is always the emergency fix we always used back in the day...and it still works if you have a heater core.

If you are ever worried about boiling over in your bumper to bumper slow go on a hot day traffic where little to no air is passing over the radiator that the fan is not pulling, or the air that it is pulling is supper heated from direct pavement and solar radiation you can follow this procedure:

Switch off the A/C and roll down all the windows. Reduce any other electrical draw that you can on the engine. Blast the heater at full fan, full heat to the floor. While roasting your toes it will drop your cooling system temperature up to the difference in the air temp and the coolant in the heater core considering the engine temp. So in theory if the air temp is 100 degrees outside, and the engine coolant is 230 and normal operating temp is 190 for your cooling system you should be able to reduce the coolant temp by almost 40 degrees if your feet can stand it. Maneuver out of traffic to some shade or pull over under an underpass and continue to dissipate the heat through the heater core until you level out at some temperature, then try to get into a traffic flow that is moving faster or change route.

Do not direct heat to the windshield, as it may burn your face, and or crack the glass with that amount of heat front and back on the slab of glass. In winter one side of the glass is colder than the other and the heat is transferred away. However in this situation it is like a baking dish in the oven.
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post #8 of 16 (permalink) Old Jun 25th, 17, 04:22 AM
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Re: How hot is too hot for the engine? (1969 350)

Question and replies very informative and interesting. Even though I do not have this problem it was sure educational for me. Appreciate the detailed responses!
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post #9 of 16 (permalink) Old Jun 25th, 17, 04:35 PM
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Re: How hot is too hot for the engine? (1969 350)

I thought I read or heard where NASCAR maybe Penske Team did a test that 209 degrees was the the optimum temperature. My new Chevy truck seems to run around that temperature.
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post #10 of 16 (permalink) Old Jun 25th, 17, 05:55 PM
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Re: How hot is too hot for the engine? (1969 350)

What stat are you running with. In Az I would prob run a 160* with a 50/50 mix of antifreeze and distilled or deionized water. Where I am I run a 180* with a 50/50 mix and it runs at 180* all day long.

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post #11 of 16 (permalink) Old Jun 25th, 17, 06:26 PM Thread Starter
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Re: How hot is too hot for the engine? (1969 350)

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Originally Posted by cv2065 View Post
Where you live shouldn't really matter. I'm in Florida myself and we're already getting 100 degree days as well. 220 plus would make me nervous. I was hitting 210 and made some changes to get back to 185-190. Now, I don't have a/c, so not sure how much that adds to the operating temp, but I would imagine that under 200 would be achievable.

Have you always been running these temps or is it something new?
Well thing is I can't really get rid of AC as that is life or death out here literally. To be honest I've never driven the car a ton during the summer months just because of the heat. During the cooler months I never get past 180. Past few days I've been driving the car for long periods of time and it gets up to ~218 and stays there no matter what. I was just curious because I truly didn't know what the MAX temp would be before overheating concerns which I don't want. I just wanted to know how much I can use the car during these summer months without worrying.
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post #12 of 16 (permalink) Old Jun 25th, 17, 06:28 PM Thread Starter
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Re: How hot is too hot for the engine? (1969 350)

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Originally Posted by COPO View Post
What stat are you running with. In Az I would prob run a 160* with a 50/50 mix of antifreeze and distilled or deionized water. Where I am I run a 180* with a 50/50 mix and it runs at 180* all day long.
Honestly not sure, had the engine rebuilt a few years back, it was done in AZ so hopefully the guy doing it took it into consideration.
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post #13 of 16 (permalink) Old Jun 25th, 17, 06:30 PM Thread Starter
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Re: How hot is too hot for the engine? (1969 350)

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Originally Posted by 69z28302 View Post
I thought I read or heard where NASCAR maybe Penske Team did a test that 209 degrees was the the optimum temperature. My new Chevy truck seems to run around that temperature.
Yeah see the problem I had was I really didn't know how hot was too hot. Most modern cars I've driven just have a gauge with a C and H and as long as the needle stays in the middle or even a little below middle you were good. Never really knew what actually operating temperatures should be or what they max out at and I wasn't sure if it varies from engine to engine thats why I came here.
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post #14 of 16 (permalink) Old Jun 25th, 17, 06:47 PM
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Re: How hot is too hot for the engine? (1969 350)

Here is some good information on Stant's website: Stant

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post #15 of 16 (permalink) Old Jun 25th, 17, 07:00 PM
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Re: How hot is too hot for the engine? (1969 350)

Dan - Well back to the basics, GM's were all way over designed and granted things get weird in deserts and mountains but in general the factory cooling system in good working order did just fine unless you were out of tune (lean mixture makes more heat) or you were towing too much crap. So check the obvious first.

Not sure how you are arriving at your temperatures but don't trust your gauge. Using a hand held infrared thermometer check your actual temp at either the sender location in the block or at the upper radiator hose thermostat housing. Does it match your senders signal to the gauge? Check the actual Ohm's it is sending the gauge. If it is OEM style factory gauge it may need a new resistor on the rear of the gauge.

Is the thermostat opening at 190 (factory specs) or 180 aftermarket tweak?
You can bench test the thermostat with a pan of boiling water and a candy thermometer. The stamped temp is the point at which the t-stat STARTS opening, up to 20 more degrees are needed to be full open for most.

Is the water pump working at factory spec or has impeller damage limited the amount of flow?
You can check the flow a couple ways using a project bucket or two and watching the flow by disconnecting the heater hoses from the core and counting flow into one of the buckets while new coolant is sucked out of another, or just watch the flow into and out of one bucket. there are a couple good threads on water pump troubleshooting in the archives. Pull a search.

Check the upper and lower radiator hoses, are they in good shape. Does the lower one collapse under heat and rpms?
The older hoses had a metal spring that kept them open during the line fill under pressure, as the rubber of the hose fatigued and spring kept it open under suction from the radiator, however the spring would rust out eventually and the hose could collapse under suction. New style ridged or ribbed hoses rarely collapse when they get old they just fail.

Is the radiator core relatively clean?
open the radiator cap and start the engine, then watch as the thermostat cycles a couple times open and closed, do you get full flow or does the core have enlarged prostate issues?

Can the radiator cap hold 30 psi still?
Shops can test the cap or listen and smell around yours when its hot. Hissing, or the smell of antifreeze is a good indication the cap is shot. Don't stick your face right near the cap in case it is defective and it blows scalding fluid or takes your teeth with it to the moon.

Is the fan belt at right tension?
Loose belt will slow the pump so check when everything is blazing hot.

If using a factory clutch fan, does the clutch work right?
Is the factory fan shroud in place and secure?
Check your tune as well.

Any one of these single items can edge your temps up. A couple of them together can have you puking fluid on the ground in no time.
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