marc9889

The problem child – 1972 C3 LS5 / 454 …. thanks in advance for the help.

The bad – High temperatures (hits 210+ with the A/C on) when idling.

The good – Stays cool at highway speeds. 40mph or more, it cools down to 190 estimated, even in Alabama 90 degree heat. Not losing any coolant.

What’s been done:
- Radiator has been taken to a capable shop and cleaned / tested.
- Expansion tank (aluminum) has been repaired (welded pin hole).
- Radiator fan shroud seal kit and radiator support seal kit have been installed.
- I’ve tried a 180 thermostat, a gutted thermostat (removed everything from the “ring” and even drilled holes in that), and no thermostat and it still gets climbs to 210 at idle. The 160 thermostat is currently in the car.
- I drained the coolant and refilled with 80/20 water/antifreeze with Water Wetter. Still 210, but it seems to cool back down quicker at driving speeds.
- The fan clutch seems to be working correctly. Even with the engine hot, I can turn the fan clutch by hand.
- I replaced the water pump, which did not have an effect on the problem.
- I used an infrared thermometer to verify the temperature at the water neck matched the gauge, and it’s within 10 degrees.
- Several different timing setting have been tried, and based on the timing light and header temperatures, I think I have it set ideally.
Equipment – Original A/C car, but currently running Vintage Air A/C, Aluminum expansion tank, original radiator (copper), 160 degree thermostat, RC-15 expansion tank cap, lower radiator hose has a factory looking metal tube (which cannot collapse), new water pump.

Questions –
- Did any 72 model big block cars come from the factory with an aluminum expansion tank? Mine has one.
- With the aluminum expansion tank, does it need the RC-26 expansion tank cap or the RC-15 expansion tank cap?
- What is the difference in the RC-15 and RC-26?
- The carburetor (original) has two small vacuum ports, both pointing toward the front of the car. Did the car come from the factory with the vacuum advance attached to the port on the driver’s side of the carburetor or on the passenger’s side of the carburetor? I’ve tried both, but the car still gets hot. Attaching to the one on the driver’s side of the carburetor makes it run rougher, so I’m guessing it has more vacuum pressure.
- Will the chin spoiler (or absence of it) affect cooling at idle? If so, why?

zwede

My '71 owner's manual states that 210-215 is normal operating temp. You may have it as good as it gets with the factory parts.

I didn't like the high temps and installed a BeCool aluminum radiator & Spal electric fans. Stays at 180F now.

Mike Ward

Yup. You're trying to fix what's not broken.

Hameister

Just called a friend of mine with a '72 C3 LS5...

Asked him what his temp is at extended idle with the A/C running.

He immediately said, around 205 to 210!

donyue

Hi marc9889, I have a couple of suggestions. My 77 - L-82 used to operate as a normal temperature of over 200, I believe the stock thermostat was a 215.

I thought it was too hot but I think the L-82 engine was designed that way to allow for the smog heads and produce less emissions. With that said my engine is no longer the stock 350 so I have upgraded the cooling system to a Dewitts rad and dual spal fans.

The two items that I would recommend for you is possibly the use of dual spal electric fans and also a high flow thermostat if applicable.

When I added my cooling system I originally went with a standard 180 thermostat but I have a high flow Edelbrock water pump. The engine ran quite hot and the electric fans turned on quite often, so I replaced the thermostat with a high flow 160 and the engine runs much cooler now.

Hope this info. helps.

Faster Rat

Since you have aftermarket air, why not put that copper/brass radiator in the box that your new Dewitts Direct Fit aluminum radiator comes in? You reportedly can see up to a 30% improvement in cooling.

Also, are you sure that your fan clutch is working properly? It is supposed to lock up as it gets hot.

I am not familiar with the '72 BB cars. Do you have a front license plate blocking some air flow? Is all the air being directed thru the radiator core, or are some of the air dams and seals missing?

cv67

Like posted nothing wrong with your car
For a BB w/ac idling on a hot day esp in a compartment like the c3 210 is doing real well. It wont hurt a thing.

Hameister

Yep, like my pappy used to say..."iffin' it ain't broke, don't fix it".

marc9889

Thanks for all the responses, and they back up what I have been reading elsewhere – that 210F to 215F isn’t dangerous for the car. I don’t disagree, but like zwede said, I just don’t like the temps that high. The 180 he mentions is much more to my liking than 215F, and my car performs much better at 180F than 215F (not to mention the heat I can feel on the floorboards, etc). I’m also inclined to believe that the higher temps reduce the lifespan of rubber bushings, plastics, and some electrical parts, so there are plenty of reasons to pursue keeping it cooler. If I can’t get there with the factory radiator, that’s good to know.

Front license plate – no. Fortunately in Alabama, we aren’t required to have one. Unfortunately in Alabama, a high percentage of the general population wears overalls and plays the banjo. I’m joking. It’s actually a great place to live.

Dewitts Direct Fit aluminum radiator – probably. I’ve tried just about everything else, so I’ll probably order one shortly. All the seals are there, but the chin spoiler is not installed. I wouldn’t think that the chin spoiler would make a difference when the car isn’t moving. Opinions?

High flow thermostat – I just put a new water pump on. Will a high flow thermostat make a difference without a high flow water pump? One step further – I’ve tested it with (see original post) no thermostat. In light of that, could a high flow thermostat improve it?

Expansion tank cap – Since I have the aluminum expansion tank, should I buy the AC RC-26 cap, or will that make a difference?

69427

Regardless, what's your actual timing at? Additionally, you're not doing your engine any favor by running that 160* thermostat.

jb78L-82

A few points:

Just because the factory manual 40 years ago says that normal operating temperture is 210 degrees does not mean that is the best temperature for your engine to run. i am sure that 210 is "normal" for your BB, but if it was me I would want to lower it a bit for a number of reasons:

1. The factory running temperature was limited by how much GM wanted to spend to lower the temp (AKA aluminum radiator, high flow water pumps etc) and the technology available at the time.

2. Running 210-215 temps leaves little margin if the car begins to get hot for whatever reason.

3. There is no running efficiencies above 180-190 degrees.

4. High temps hurt performance above about 190 degrees.

5. High water temps really tax the oil- more on that later.

6. High water temps in the late 70's was all about emissiions compliance.

My 78 L-82 4 speed routinely ran 225-235 degrees with AC on and 90 degree ambient temp when new since GM had no other way to get the L-82 to pass emissions at that time. Quite frankly, it was ridiculous-the car was an oven!! GM even changed the 79 temp gauge to 225 at 12 O'Clock from 200 in the 78 due to customer questions about the operating temperature of the car-the needle of the gauge was 3/4's to the red zone, normally. Years of trial and error, resulted in my current configuratiion of Dewitts aluminum radiator and a Stewart Stage 2 aluminum water pump with a high flow thermostat resulting in a running temperure today on a 90-95 degree day of 180 degrees-GM mechanical L-82 fan and GM L-82 fan clutch. The car has never run better!

When the car ran 235-240 on really hot days, the oil temp was 250-260 which is very marginal! I have an 81/82 oil temp gauge where the clock use to be. If your car is an automatic with the trans fluid cooled by the radiator, running 210-215 degree water temp means that the trans fluid temp can never be less that 210-215 which again is very marginal on the fluid and will shorten the life of the tranny.

Although 210-215 is probably pretty normal for a BB, there are benefits to running lower temperatures if you want to go that route.

Hope this helps!

marc9889

JB78L-82, Do you mean regardless of temperature?
36* @ 3000 rpm.
I'm not inclined to believe the 160* thermostat will have a negative effect on the engine because the temps climb to 180* (or more) just as fast as if I had a 180* thermostat in it. In cold weather, that may change, but for now it isn't a factor.

cv67

The DeWitts will be a nice effective upgrade and although the dam doesnt do anything at idle it will cool quicker as you move meaning once back at idle youll probably be running a lower temp and not fighting to bring it back down as hard.

Mike Ward

Which renders the discussion about 'performance' irrelevant.

jb78L-82

Not sure what you mean by "regardless of temperature". Yes, my engine has 36 degrees timing all in by 3,000 RPM.

marc9889

jb78L-82 - Your original post: "Regardless, what's your actual timing at?" I was asking if you meant regardless of temperature.

Tin_Can_Terminator

There is some stuff that you can put in the Radiator that helps cool even more than normal Rad fluid. You can get it at Parts store.

TCT

69427

That's incorrect.

jb78L-82

That came from 69427-not me.

qwank

99% of new cars run at 210 degrees