[Bobalong]

Talking to my mechanic the other day and in a casual conversation asked him
" How hot can an engine get before it becomes an issue?"

He his response was that most electric cooling fans in cars come on right at 130 deg. So probably 140 is the limit before it gets serious.

I get puckered when my 400 engine gauge hits 125 -130 with A/C on at a traffic light in the summer. Not sure when the dash light is supposed to come on but it never has after start up.

When these cars were new, many never had gauges, only idiot lights, wonder how many 140+ deg engines were just driven as long as the light never came on, or just as long as it went off after traffic started to move and some air went across the radiator.

Oil quality has improved dramatically since the 70's, Maybe this temp issue has been overrated and promoted by the industry manufacturing aftermarket fans, radiators, and magic potions to add to the coolant.

Just food for thought.
I'm still running a GM flex fan 4 core radiator and off the shelf anti freeze. All the factory shields and things to direct the air thru the radiator are in place.

Just my 2 cents, results may vary, proceed at your own discretion,

[ELKHORNAOG7]

Are your sure he said 130-140 deg.-----BOB

[66beaumont]

Think he meant 230. I work on lots of heavy equipment with electric clutch fans,usually engage about 225 or so

[Tom Vaught]

Believe it was just a typo on the post.
His Brain may be relating to ambient temps and mechanic is talking in coolant temps 160 degrees F to 240 degrees F.

If he was talking Degrees Celcius, 100 degrees C = 212 F and 130 degrees C would be really HOT.

Tom V.

[TedRamAirII]

Originally Posted by 66beaumont

Think he meant 230. I work on lots of heavy equipment with electric clutch fans,usually engage about 225 or so

+1 Most GM cars, the electric cooling fan comes on at 229f with the a/c off. When the a/c is on, the fan is on when commanded when high side pressure reaches a limit to turn the fan/fans on. I dont have that particular pressure on hand. I dont call a car actually "overheating" until it pukes coolant from the radiator cap or reservoir. With coolant under pressure say, at 16 lbs, the boiling point is raised 3 degrees for every pound, so coolant/water isnt going to boil until its 260f. I have not tried it, I have a 160f thermostat in my car, I am going to try a 190f. At highway speeds, my car runs right at 165-170, but at stop lights, will creep up and then when moving again will come back down. With a 190f thermostat I am thinking the larger differential in ambient temp and a hotter engine temp, the cooling system should be more efficient. What do you think?

[Bobalong]

Originally Posted by 66beaumont

Think he meant 230. I work on lots of heavy equipment with electric clutch fans,usually engage about 225 or so

Yea, brain fart on the temp. Meant 230f

Other posts here kinda support my suspicion on the hyperbole on overheating, and the need for more exotic means beyond factory stuff.

However I certainly would upgrade if say for example I had to replace the radiator or a broken fan or water pump. But wouldn't start replacing stuff chasing a problem that doesn't exist in a street driven mostly stock muscle car.

I remember back in the day when our state police were driving those monster Dodge Polara Land Yachts circa 73. See them working an accident, motors idling for hours, hood popped to let some heat out.

[Schurkey]

The "HOT" light on the dash was often triggered by a temp switch that wouldn't turn on until 240--260 degrees.

It's not "overheating" unless the coolant is boiling. HOWEVER, an engine at idle or cruise should run within a few degrees of the thermostat rating unless there's an electric fan or two, and then things depend somewhat on the thermal switches governing the fan. With a standard, flex, or clutch fan, if the coolant is more than 20 degrees above the thermostat rating, the cooling system is insufficient, or the engine is producing more heat than it should.

If the coolant temp is ~20 degrees above the thermostat rating, the thermostat has lost control of engine temperature.

[Chris65LeMans]

I'm glad to see this discussion. I had thought that the general consensus on this site, which I don't agree with, is that one should spend thousands of dollars and dozens of weekends in an attempt to keep their car running below 180 at all times.

My owner's manual says this about heat, and only this: (I'm paraphrasing): "If the temp hits 245, shut down and diagnose."

I'm asking my engine to do a lot more, (through porting, stroke, bigger cam, etc.) then it originally had to do, so I think it's reasonable to expect it to run hotter.

[Schurkey]

Originally Posted by Chris65LeMans

I'm asking my engine to do a lot more, (through porting, stroke, bigger cam, etc.) then it originally had to do, so I think it's reasonable to expect it to run hotter.

No, it's reasonable to expect to have to increase the cooling system heat-rejection capacity.

[indymanjoe]

My 400 .60 over xe cammed 96 d-port heads runs all day at the track ,hot lapping and i mean back to back to back to back etc on the road freeway driving 3000 rpms at 70 mphs with some bursts to 100 Never ever gets over 170. Idling in woodward dream cruise traffic never see's over 170. My self i dont understand the need for aftermarket cooling stuff (snake oil). My water pump is stock (properly clearance d) radiator is stock,stock clutch fan,nothing aftermarket at all. Maybe a "track race car" built to the max is different but dont MOST of us drive our cars? I just dont understand why so many have issues.

[Formulajones]

My feeling on the new stuff running so warm has more emphasis on emissions, as the hotter engines burn off more hydrocarbons, cats work more effectively etc... Not that running them hotter makes for a better running engine, per say, cleaner....sure.

Most of us building these classics are pushing the pump gas envelope. Lets face it, pump gas sucks and is getting worse. Trying to make even just decent power on it with 10:1 - 11:1 compression takes a sharp tune and close control over all parameters, including engine temps. Even some 9:1 engines can struggle.

I haven't seen a car come in here yet, that makes decent HP on moderate compression ratios, with a decent timing curve, that runs around on pump gas with the engine at 220-230 degrees without complaining. You try that out here in the AZ desert heat and you'll find yourself in trouble.

What I find in most cases, keeping the engine at or below the 190 mark has been fairly safe on pump gas with decent timing curves. I'm able to do that with stock cooling systems that function properly.

Many examples here. My fathers 571 is an extreme example with 10.84:1 compression, runs 91 pump gas, completely stock issue cooling system. The car generally runs between 175 to 185 most all the time without complaint. I'm going to bet trying to make this engine run way up at 220-230 would likely end his day early.

One daily driver we use, is 11:1 with an iron head, runs on 91 pump, and it drives around in the AZ heat at about 175 most all the time. Stock cooling system. I would be a fool to run this engine at 220 degrees, damage would result.

To get away with that I'd want a steady diet of 110 octane in the tank. Not feasible in a daily driver these days.

What people also don't consider when wanting to run these high engine temps is that everything else is also running hotter. The trans for one. But what I'm more concerned with are the other components under the hood. Heat soak and vapor lock is a biggy when it comes to pump fuel. Something new cars don't have to worry about with fuel injection and 60+ psi of fuel pressure.
People want to make their classics run at 220 degrees because that's what all the OEM's are doing and then wonder why it has vapor lock and heat soak issues, lol.
I'll stick to my regimen, since I push the pump gas issue, I'll keep my engines running on the cool side and keep things safe.

[HWYSTR455]

So C.A.R.B. began in the late 60s, EPA in the early 70s, and we all know what happened to performance in the 70s.

What bothers me most these days is MPGs. Why do new cars suck gas? The tech is there, these econo cars should be over 60 MPG. Shoot, some of the 60s and 70s car get better MPG than some new cars. Not even going to bring trucks into this topic, it's just ridiculous what MPGs they get.

Anyway, it's obvious the reasoning for higher operating temps are for emissions purposes. It's a shame that the EPA requires certain emissions devices be present, and not set standards for actual 'emission' of harmful substances. If they left it up to the engineers, I bet not only would cars perform better, but emissions would be considerably lower.

People need to understand that a 'performance' engine = an 'efficient' engine. And visa-versa. If you make the same power with less fuel, what would you call that?

.

[Formulajones]

Originally Posted by HWYSTR455

So C.A.R.B. began in the late 60s, EPA in the early 70s, and we all know what happened to performance in the 70s.

What bothers me most these days is MPGs. Why do new cars suck gas? The tech is there, these econo cars should be over 60 MPG. Shoot, some of the 60s and 70s car get better MPG than some new cars. Not even going to bring trucks into this topic, it's just ridiculous what MPGs they get.

Anyway, it's obvious the reasoning for higher operating temps are for emissions purposes. It's a shame that the EPA requires certain emissions devices be present, and not set standards for actual 'emission' of harmful substances. If they left it up to the engineers, I bet not only would cars perform better, but emissions would be considerably lower.

People need to understand that a 'performance' engine = an 'efficient' engine. And visa-versa. If you make the same power with less fuel, what would you call that?

.

I agree on all counts. Given all the technology, I'm really not all that impressed with fuel mileage on new cars. Manufactures are being choked with regulations.
I'm doing nearly as well, and even better in some instances, with my classics using a carb and points ignition systems, and no overdrive.

[HWYSTR455]

Yeah. A guy has like an early 70s duster, slant 6, bone stock, but he's 'tuned' it. He says he gets in the 30s MPG with it.

I had an AMC Sprint, inline 6, that thing would fry a tire, and was getting in the 30s with that. All I did was carb and ignition tuning, and remove the cat.

My 67 Coronet convertible, 318, 323 rear auto car, was getting high 20s/low 30s in that, and it would do low 14s in the 1/4.

I just don't get it, it's like they on purpose make them eat gas. I just can't see how they can't be getting better MPG.

Well, the next 10 or so years will be interesting, many countries have goals for alternative and electric vehicles. Maybe this will help improve the refinement of gas? Will probably drive the price up.

.

[SRR]

Modern cars also have knock sensors. They also adapt to crappy fuel. Old cars don't need to run at 200+ to run good. Some how my 462 Buick Skylark runs at 180-190 degrees with a 7 blade fixed blade fan and four core radiator no matter what temp it is. I'll take this "problem" any day!

[coonhunter70]

220+ is too hot

[Schurkey]

Originally Posted by coonhunter70

220+ is too hot

Too hot for WHAT?

It almost certainly too hot for optimum power. (although if the intake charge could be kept cooler, while the block ran 220, that'd be great!)

It's probably too hot for detonation resistance.

It's probably near-optimum for emissions control; at least for HC and CO.

It's probably near-optimum for reducing engine wear and oil sludging, IF the oil temperature is not too high. Coolant temperature and oil temperature can vary considerably.

It's probably near-optimum for fuel economy, if the fueling system is engineered to work properly at that temp.

It's not hot enough to cause engine damage UNLESS it promotes detonation.

[coonhunter70]

I suppose i'd have to agree with you on those points it's just hotter than I like to run these old engines.

[64cabro]

I realize this thread it old, but I always look for "old" threads before asking a question .... but hopefully I get some feedback.

I'm not Mr. Knowledge when it comes to this mechanical tech, just know enough to know that I need to be careful and not screw something up.... which leads me to question how hot is too hot. I live in Central FL and right now is not necessarily the most enjoyable time to be out hot rodding.... hot air, hot pavement, hot sun, no AC (wha, wha, wha right?)

My Goat has a 455 from 1970 Bonneville. Only had the thing for a few months, and haven't driven it much, but only recently started paying attention to the temp gauge. On the day that raised concern a week or so ago when I decided to pay attention to the temp gauge and it was around 220 degrees and I realized that I have no idea "how hot is too hot" and if I needed to shut it down or not. Reading this thread, I'm somewhat comforted by seeing some of you guys say 220 is OK, but worried when others say 220 is too hot and others talk about driving in AZ and never getting up to 200.

As far as I'm aware, the radiator, fan and pump would be considered stock, though they're all new and rebuilt thanks to a pretty top-quality resto-mod by my dad that he completed a few years ago. "What's wrong with my goat?" is what goes through my mind when I think of why it's not running below 200. I could rationalize that cooler is better, but sounds like that's not NECESSARILY the case.

Looking for dad-type advice on when I need to be concerned, but I'm guessing some answers might include the words "it depends" on X, Y and Z.

Any and all feedback will counted as value and appreciated. Already grateful for the exchange below! I asked dad and he said he can't remember.... he's suffering medically and recalling technical facts and answers like he once could is no longer his strong suit....unfortunately. He did suggest I turn to the forums to read up and ask questions!

[Tom Vaught]

1) I would verify that the temp gauge is truly reading 220 degrees F.

2) I would find documentation or remove the thermostat and test it in water to
see when it opens and controls the flow of water.

3) I am assuming that the radiator, fan and pump would be considered same as stock
and operating properly for the time being.

4) Since you are located in Florida, I would find documentation on when the coolant was
last changed. This would be one of the initial steps before messing with the engine (thermostat).

5) You have only had the GTO a few months but the car has apparently been in the family for a "few years".
How much driving did your dad do with the car before you acquired it?

Post up and maybe we can help you either not worry as much or be able to get the temp
of the engine at a temp you are more happy with.

Tom V.