What is normal water temperature for a 455 engine with A/C engaged?

Need some help here. I understand that Buick 455 runs hotter than most engines.
This is my first Buick BB.

What is considered normal water temperature with A/C running, either idling at a stop light or in congested traffic?

The shop I have working on my Buick go into a panic mode when the water temperature gets to 220* during these events.

Under normal cruising speeds (60 mph) with A/C on, water temps run around 185-190.

I guess my question, 220* too high?

 

It should be 5 to 10 deg max above your thermostat rating. Any higher and the cooling system has lost the ability to regulate temperature

 

I had a 160* (high volume) thermostat installed.

I had a new thermostatic HD fan-clutch installed.
I have the original 7 blade fan and fan shroud.
Checked the water pump and crank pulleys. Both are correct for my 1970 Buick GS 455.
Installed a new radiator (should have installed a 2-core Aluminum model).

Have T/A's High Volume water pump being installed today along with Evans coolant.

I believe this will cure the temp problem, just needed to know what water temp I should be at idle with A/C engaged.

Thank you very much. VET

 

Should be the same as the thermostat you have installed. Idling is a poor test. Drive the car hard for a bit after its warmed.

 

165 is too low to begin with, 185-195 is appropriate I think.

 

Do you have the correct 18 inch seven blade fan clutch, and fan shroud ?

 

Yes I do.

Speaking of thermostats, in the owners manual, Buick calls for a 180* thermostat. If my temp is suppose to be max 10* degrees above the thermostat rating,
My high temp would be 200*.

Now that I'am using a 160* thermostat, my high temp should be 170*.

This is confusing & doesn't make since to me. Something is off here. VET

 

Correction, 190* using a 180* thermostat. VET

 

Where the high water temperature shows up is only when the A/C is engaged.

Without A/C, temperature runs normal. Go figure!

 

Max temp is what the car is stable at.

Making the claim that "10* above the max temp the system has lost control" is absurd, if the temp is stable at greater than 10*.

The thermostat controls minimum operating temperature not max.
Once the open temp is reached (and it typically begins opening several degrees below, but not fully open until several degrees above "listed" for the thermostat) that is the minimum temp the car is supposed to be operated at, once the thermostat is fully open, the car will run at a stabilized temp from the combination of coolant, capacity, radiator effective ability, shroud, fan, water pump, pulley sizes, engine load, RPM, proper tune, ambient temp and speed of car, AC adds the impact of the condenser restricting airflow and the amount of heat rejected into the air cooling the radiator, and added engine load to run the compressor. All of these are factors that have to be understood and considered.

My '64 Skylark (nailhead) has a 160F thermostat and on hottest days (100F) and in stop and go heavy traffic it can reach 200F and no more, and on cooler days (75-80F, it can run dead on 160* even with the fans off above 25 MPH.

My '68 (BBB) can idle all day long on the hottest days and never break 180F (ran for more than 3 hours during test and tune, and making runs).

Both cars are set up identical radiators, fans/shrouds and temp switches.
The '68 has aluminum heads, intake, and ceramic coated headers, that factors in on the cooler idle.

A lot of racers run with no thermostat, and some run with restrictors sized to provide them a steady max temp.

There is a lot of info (some bad) about things like "not having coolant stay in the radiator long enough to cool". But the science is the greatest heat rejection to the cooling system and then to the atmosphere is the greatest when the delta is highest. So, much more heat is rejected into the atmosphere from the radiator when the ambient temp and the coolant temp are at their highest.

The faster that hot coolant gets in the radiator, the more heat will be rejected to the atmosphere, and the faster that coolant gets back into the hot engine, the greater heat will be rejected to that coolant, and the "loop" is more heat liberated.

Slowing the coolant, lowers the amount of heat liberated over time, as less heat is removed as it is cooling over time.

The "temp light sender is set to about 245F degrees, so "too hot" is well above 200F.
Radiator caps at 16lbs facilitate no boiling up to 265F degrees.

So, these engines were designed and capable of running at 220-230F and not suffer failure.

Yes, performance may be impacted with fuel flashing off in hot intake, carbs and fuel in lines heat soaking, and a hot engine feeling "down". But that is not the same thing as suffering damage.

But, all that said, if the car does not "perform well" above even a safe level (say around 220F), then looking to solve that high a temp, is not a wrong thing to do.

But people obsessing over a car running 200F with AC on triple digit days is simply needing to understand the system and what is or is not "too hot" (unsafe) operating temps.

And a correct coolant around 50/50 for most optimal cooling and protection to the system.

 

Typically 20k BTU liberated by radiator.
The condenser liberates about 6k BTU in front of the radiator, potentially raising the effective ambient temp about 25% greater then a car with no AC.

So, your AC bringing temps up 20-30 degrees, is not unlikely.

 

Also, AC on can slow idle speed, causing both less coolant flow and different output voltage from alternator, which affects electrical gauges.

 

Great information, thank you so much TrunkMonkey. I now have a much better understanding.
My radiator caps at 15lbs on the 1970 model GS. I noticed your 68 BBB caps at 16lbs, not sure if this is a big difference or not.

Let me give you a bit of history. When I bought this Buick in 2021. Along with the build sheet I also got a ton of mechanics notes and service/repair receipts and information too.

(1) Mechanic note: Recommend replacing radiator, engine is overheating.

(2) Mechanic note: Engine detonation at all rpms.

Of course, none of these issues were revealed to me during the purchasing process. Lying Dealership.

After months of work and $$$, we have finally cured the detonation issue.
The second issue (overheating) should be cured tomorrow (I hope).

Reason why I posted my question is because I have been given all kinds of possible reasons WHY I'm having overheating issues.

Thank you for helping to me to understand these issues. You have been a great help. VET (Navy)

 

Thanks Max, I noticed that. When I turn-off the A/C, the idle increases and of course with the A/C off the water temperature also goes down. VET

 

Has your car actually ever overheated? As in, the light comes on HOT, and the coolant is expelled from the radiator?

 

Good question, answer, NO. The shop won't let it over boil because if they hurt the engine, they are liable to repair the damage.

When the engine gets to 220* in less than 2 minutes at a stop light, they panic and turn-off the A/C and increase the idle.

I have a Dakota digital dash in my Buick. No Red Light. It's easy to see the water temp in degrees.
They checked to see if the digital gages are accurate, and they are. VET

 

Did your mechanic check the distributor? Make sure it’s working correctly with initial and total timing?

 

My 430 runs consistently at 185. In very, very heavy traffic, think accident or beach traffic, on a smoking hot day, it will climb to almost 210. If I can get it over 10 mph it will cool right down to say 200 and in 5 minutes at 35 mph it will be back to 190. To me, there’s a few things you need. I have a good water pump, your TA is a great choice, a high flow tstat, fan shroud (for lower idle temps) and a two row, wide row, aluminum rad. To me it’s the last bit that matters most. If the radiator isn’t effective, all the other bits are not enough. If you have an old rad, that’s probably where I would focus my attention. @TrunkMonkey gave a superb explanation of why the tstat is a total red herring. I see no reason why a car should hit 220 at a light after 2 minutes. What happens if you get stuck in a traffic jam, seems like you would be cooking the motor.

 

Distributor is all new.
It's an MSD ignition.

Believe me, we have been all over this engine for a long time now.

 

Believe me when I say, everything is brand new, including the radiator, even if it's not a aluminum model.

I cleared the radiator model with Todd Miller before I bought it.
The entire cooling system is new and accurate to the model
of my car.
Hopefully TA's High performance water pump and Evans coolant will take care of this problem.

Maybe, I don't have a problem?
It's never boiled over and the shop tells me that my digital temp gage measures water temperature 10 degrees higher than what they measured.