[78w72]

the factory T-stats were 195* in most these cars. reading some of the "overheating" comments on here or out there, many people think some kind of damage is going to happen at 190-205* then start to do all kinds of crazy unnecessary things.

even at 100-200hp above stock, the factory cooling systems should be able to support that, if it & the engine are in good working condition... everyone did it before aluminum radiators, electric fans or high flow water pumps were available.

[OG68]

Considering the over temperature idiot light switch is set at 248*, apparently Pontiac wasn't to concerned about running at 200-220* either.

Nice thing about idiot lights; Ignorance is Bliss. LOL

[Formulajones]

While I didn't care so much 35-40 years ago, we do have to keep things in perspective these days.

Biggest problem now is the crappy fuel everyone is trying to run these cars on, that also feel they really should be running these cars at or above 200 degrees, and then complain about vapor lock. Todays fuel just isn't going to tolerate that at all when you only have a fuel pump that delivers 6 psi of fuel pressure to a carb.

Those 2 scenarios just don't play well together. So I tend to keep my cars running quite a bit cooler than that. Plus the fact that I'm generally running these things with quite a bit of compression for the fuel being used, so there are some things that need to stay in check to make that work well enough to drive them. Otherwise owning and driving a classic car is just going to be a miserable experience and then we get all these wives tales started on the internet that really doesn't help anyone.

But the big point I like to make is that not only am I making bigger HP run cool, I've got them running cooler than the factory ever tried to do, and doing it with the stock issued OEM stuff. You don't really need to reinvent the wheel.

[OG68]

Also came across this Dealer Bulletin regarding overheating. Temperatures up to 260* are allowable without damage.

But I fully understand circumstances are different these days.

[TRADERMIKE 2012]

Originally Posted by HWYSTR455

So, curious.

How many who say they have no overheating issues with stock setups have AC?

How many have driven those AC cars in 100+ degree weather in stop & go bumper to bumper traffic for extended periods of time, like over an hour?

I daily drove my car in those conditions, and, I needed to switch to electric. I had a legitimate reason/need to switch. Still stand by the statement, if you don't have a reason to switch, don't waste your money & effort.


.

Mikes Reply:
I agree with your argument first off and I skimmed through your post about "1970 GTO Judge Tribute" and it is a well-built Vehicle; you should be proud and I am sure you are. The video on Valve train Geometry, I found most Informative due to the fact that everything else I read was different?

My 1981 Camaro Z28 ran @ 225 degrees F with the AC off, all the time.

[Formulajones]

I didn't see that post but since the question was asked I do have one classic here that fits that scenario. My Chevelle specifically, is a factory AC car. I run a 600hp 454 in it, and have installed 4.10's in it no less. For years I had the AC working and the hottest it would get in slow traffic and idle situations was in the low 190's but would stay in the 180's while moving. Did this with the stock cooling system, shroud, clutch fan, with the only addition being a new 4 core copper radiator at the time. I probably had the car for 25 years at that point without a problem.

About 10 years ago when the radiator sprung a leak I swapped it for a 2 core Griffin aluminum radiator with 1 1/2" tubes. That dropped the temps a few more degrees. I left everything else the same. I drove the car another 5 years like that.

These days now living in Arizona I found I was using the AC less and less, even living in Arizona with 100+ temps, so I decided to put the car on a diet and remove the AC components. Oddly, it didn't change the temps the engine runs with the condenser out of the way.

[dataway]

I think when you compare the difference in fans, air sealing and radiators used in AC cars compared to non-AC the difference should easily make up for the added heat coming from a condenser.
When you think about it, AC does add some heat, but little compared to the heat the engine normally produces, the extra load is also pretty small, and the potential for reduced air flow should easily be compensated for with the larger fan and radiator.

[Formulajones]

Originally Posted by dataway

I think when you compare the difference in fans, air sealing and radiators used in AC cars compared to non-AC the difference should easily make up for the added heat coming from a condenser.
When you think about it, AC does add some heat, but little compared to the heat the engine normally produces, the extra load is also pretty small, and the potential for reduced air flow should easily be compensated for with the larger fan and radiator.

Yep, and AC cars generally have a much different pulley ratio overdriving the water pump by quite a bit too. which also turns the fan faster.

[ZeGermanHam]

Originally Posted by Formulajones

Yep, and AC cars generally have a much different pulley ratio overdriving the water pump by quite a bit too. which also turns the fan faster.

Yep, when I finally got an A/C pulley for my car and compared it to my non-A/C pulley, I did the math and found that the A/C pulley spins the water pump about 23% faster than non-A/C. That's a big difference, both for fan speed and pumping coolant.

[78w72]

im not suggesting to do this, but what about the under drive pulleys you can buy for pontiacs & other brands? many people over the years have claimed pontiacs want slower moving coolant to remove more heat.

[JLMounce]

Originally Posted by 78w72

im not suggesting to do this, but what about the under drive pulleys you can buy for pontiacs & other brands? many people over the years have claimed pontiacs want slower moving coolant to remove more heat.

I believe this is internet folklore.

The transfer of heat in convection which is what is being done with a radiator does have some dependencies like the type of material, viscosity of the fluid etc., but for all intents and purposes, for this discussion it transfers near instantly.

Slowing down the rate of fluid flow through the radiator does not jive with the accurate and common sense based methodology that:

1. If heating occurs at idle or low speed, air flow is to blame
2. If heating occurs at speeds above 30 mph, coolant flow is to blame

The factory used smaller water pump pulleys on AC cars because of the need for extra cooling capacity. You're doing so at the cost of parasitic drag on the engine.

This is also why an underdrive pulley would be the opposite of what you want if you're having cooling issues. It will drive the accessories, including the water pump slower.

[Sirrotica]

There is another reason to spin the water pump at a higher speed, it increases pressure in the cooling system to help eliminate steam pockets in the cylinder heads.

As far as water traveling too fast, and a restrictor helping to cool an engine better. The absence of a thermostat lowers the pump pressure allowing steam pockets to form more easily, so if you put a restrictor in the thermostat housing it also eliminates the steam pockets by raising pressure. Having a restrictor, or thermostat, plus speeding up the water pump raises pressure. These 2 items work in conjunction to stop overheating.

This is where the myth starts about slowing down coolant, if a casual observer sees a restrictor helping the O/H problem they "assume" that the water is traveling too fast to reject heat. If that theory had any merit the coolant also wouldn't pickup heat from the engine, but the coolant definitely has no problem picking up heat as it passes through the block, therefore that myth is busted.

Electrons is how coolant releases heat into a heat exchanger/radiator, so as JL has said, it happens instantaneously. When steam pockets form the coolant is in a gaseous state, and steam/gas is a much poorer conveyor of heat.

Steam pockets are the same problem that can cause a nuclear reactor to melt down. If the dome is steam bound and the water can't get to the core to cover it, more steam forms multiplying the problem. Venting steam in this situation is the way a reactor is saved to allow liquid to cover the core again.

When the hottest spots in the automotive cooling system, the cylinder heads become too hot, steam forms, and more pressure and flow is how it can be taken back under control, or stopping the steam from forming in the first place.

[dataway]

As an ex-Navy Nuke ... all I have to do remember the formulas for heat transfer in a fluid system. Flow rate is one of the variables ... increase flow rate you increase heat transfer. I don't think I ever in my life saw a system where this was not the case.

Some people might get confused by the fact that with higher flow rates water exiting the radiator may be at a higher temperature than water flowing at a slower rate.

The total heat removal is still higher because each lb/mass of water is capable of carrying away a certain amount of heat, the more lbs of water (more flow rate) that moves through the radiator, the more heat will be removed. But the outlet temp may very well be higher than with a slower flow rate (this is because the air flow is constant)

Another advantage to a higher flow rate is that if the average temp. of water flowing through the radiator is higher, it has a greater temperature difference to ambient. This increased "Delta T" creates more efficient heat transfer to the air. (Delta T is another variable in a standard heat transfer equation). The factory choose radiator size and design assuming a known range of Delta T between coolant and air temp. Throw in a 160 thermostat and it can lower that Delta T out of an efficient range (depending on ambient conditions)

And yet another advantage of higher flow rate is more turbulent coolant flow, which produces more efficient heat transfer as it causes good thermal mixing and helps prevent the steam pockets as mentioned by Sirrotica.

As my old Navy Thermodynamics professor used to suggest ... if you are in doubt about a theory ... take it to a ridiculous extreme and see how it works out. So if SLOWER flow created better cooling ... then slow it down by a factor of TEN and see how that works out for you. I'm guessing it would work out far worse than increasing flow by a factor of ten

[67Fbird]

[QUOTE=if you are in doubt about a theory ... take it to a ridiculous extreme and see how it works out.[/QUOTE]

alot of truth is this statement^^

[OG68]

I remember those lectures Data, although my memory isn't as good as yours.
NPS Mare Island 71-72.

[dataway]

Jeez, NPS Mare Island?? That was a long time ago
So you were freaklin Slide Rule days? I was first year of the calculator ... we showed them off like a pretty girl friend, they were not cheap back then.

I was NPS Orlando 78.

I still have all my NPS handwritten notes ... shhhh, I know I wasn't supposed to keep them.

[HWYSTR455]

Yeah, I was an AE, on A6s, can somewhat relate! A6s,that shows my age!

.

[OG68]

My dad was a surveyor so I was very familiar with slide rules. Did great with the math but Physics was my weak point and I was dropped after 4 months of NUC school. ( I didn't take notes like Data did lol)

CVA 19 is where I ended up during my first of six enlistments. A4s and and F8s.
The Cats, arresting gear, and 400 HZ generators were my specialty. But all that was 50 years ago.

[HWYSTR455]

WOW! Salty! F4 & F8, F8s are LOUD. I was on the Nimitz when it was east coast, thing was a Cadillac compared to the Hancock! Heheh! Thank you for your service!

.

[TRADERMIKE 2012]

Originally Posted by Formulajones

I didn't see that post but since the question was asked, I do have one classic here that fits that scenario. My Chevelle specifically, is a factory AC car. I run a 600hp 454 in it, and have installed 4.10's in it no less. For years I had the AC working and the hottest it would get in slow traffic and idle situations was in the low 190's but would stay in the 180's while moving. Did this with the stock cooling system, shroud, clutch fan, with the only addition being a new 4 core copper radiator at the time. I probably had the car for 25 years at that point without a problem.

About 10 years ago when the radiator sprung a leak, I swapped it for a 2 core Griffin aluminum radiator with 1 1/2" tubes. That dropped the temps a few degrees. I left everything else the same. I drove the car another 5 years like that.

These days now living in Arizona I found I was using the AC less and less, even living in Arizona with 100+ temps, so I decided to put the car on a diet and remove the AC components. Oddly, it didn't change the temps the engine runs with the condenser out of the way.

Mikes Reply:

I would say your radiator was getting plenty of air through the condenser core.