I finally got a digital reading of my engine over several days.

It shows 200-203. With a 180 Thermostat I'm guessing this is a good temp? My gague on the dash shows it dangerously high. Could be a bad gague?

- Mark

It would help to know where on your engine you took the readings. You should measure the temperature at several spots across and down the radiator core with the engine running. If the 200-203 readings were taken right after doing a July 4th parade at a crawl on very hot day, it might be acceptable but otherwise not. A 180 degree thermostat should keep the temperature of the coolant at the top of the core at about 180 degrees.

I took the readings front, middle, and back of the motor.
Just came off the highway (did about 80-90 kms) for 20 minutes.

- Mark

Had you shut it off, or was it still running? Temperatures of both coolant and engine climb significantly after the engine is shut off.

It was still running before I tested the engine. I'll check the Rad the next time i'm out. I didn't test that at all.

- Mark

G'day all, I agree with Owen that the temp can and generally does rise significantly after a run where the engine is fully up to temp. The old saying is that 25 percent goes to the tyres, 25 percent to the exhaust, 25 percent to the water and 25 percent to the oil. After a longish run the residual heat from the oil and cylinder block will elevate the static temp of the water. It is particularly noticeable with a Packard where the temp is taken from the back of the block. A modern car takes it's temp from the top of the thermostat housing area where it is reasonably cool. I recall that Packard changed guage makes in the middle fifties to get one which read lower, to the extent that if the gauge ever went halfway, you were in big overheating trouble. I would fit a 164 degree thermostat to your engine. If you are running unnecessarily on a premium unleaded, this will raise your operating temp around 10 degrees as opposed to running on regular unleaded ( in my experience on old motorbikes)

My temp guage always sits between the E and the M in temp.. are you going to Barrie this weekend for the meet there?? I will be going there tomorrow , and do some vending, will be in the orange field with a house tailer with a big Packard Logo on the back...

Mine is sitting past the "P" a little bit even when idling.

I'm planning to. I don't have my regular car, so I hope the old girl is up for the challenge. Good thing gas prices have dropped.

I'm on the hunt for flat headlights and the air filter.

- Mark

Once the car is warmed up the temp should always be above 180, that is what the thermostat is for, to keep the temp above 180.

A temp of 210 or 220 would be normal. If you notice the temp stays steady when driving along but rises in traffic and when climbing a long hill it could mean your cooling system is marginal, in other words the rad may be partly clogged, the fan not working correctly or something.

If the readings are that low,200-203, and that even front to back, it indicates your cooling system is excellent. Your thermostat, rad, water pump and cooling fan must all be doing their job. And your engine block is not clogged with rust and scale, and the coolant is being evenly distributed front to back.

Your gauge may be faulty. What does it read when the engine is dead cold? The needle should be way below the bottom mark.

I got two cents! Please allow me to suggest two things: Maintain your radiator cap. Each pound of system pressure increases the boiling point, three degrees F. (If you have a 5# cap, 212 + 15 = 227 degrees boiling point.) If you use a 7# cap, boiling point raises to 233! Contrary to many beliefs, running hot (190 degree thermostat) is the optimum engine temp, and it will entend the life of your engine as a system. Running a cold engine causes excessive wear. So, bear in mind, your car was designed for a specific thermostat/radiator cap. Having said that, NEW cars use a very hot thermostat, and a sixteen pound rad cap. That's one reason 200,000 miles is very normal for a modern car.

My second suggestion is to maintain your V-8's heat riser valve, in your exhaust.
When they fail, they usually stick shut, forcing hot exhaust through your intake manifold, and over-burdening your cooling system. (That's great for speeding warm-up in zero degree weather, but not after it is warm.)

Mark:
Your temperature gauge will read high as the standard thermostat that came in the car was 150 degrees with an optional thermostat of 160 degrees.
John

It sits right on the white line for "L" when the car is stone cold.

I'm thinking the gague might be shot. Could also be the fuse on the backside as well? The one for the clock blew a week ago and needs to be replaced.

- Mark

Rad cap has been an issue. They lost the cap when the rad was re-cored. I have a 7lbs Canadian Tire one and had to add 3 gaskets to it to form a tight seal. I'm confident that this issue is no more as i've had no coolant loss once i did this last week.

I'm worried about putting a higher number cap. I lost a rad last year with a 13 lbs, the top tank exploded.

- Mark

So I should lower the thermostat to a 160, which will start the coolant moving though the engine sooner?

Ask a good radiator shop. They buy new radiators and guarantee them. All radiators have a pressure rating, and they might have your original cap spec's.

Lowering your thermostat temp might start flow earlier, but the real issue is your cooling system's capacity to transfer heat (in BTU's per hour). To be efficient, you must start with a sealed system, have good coolant and air flow, etc.

If you don't trust your gauge, use a good cooking thermometer. They're cheap, they rarely lie, and they can tell you a lot about what's really going on. You can hold it in place with a rag, just to get a reading.

I guess I have to disagree with the statement of having to heave a sealed system to be efficient. How about all the cars manufactured before pressure systems like my 1934 Eight?

Yes, a sealed system is needed only when the radiator is too Small to cool it properly alone, as modern rads are. Higher pressure, in sealed system, lowers temp also.
Water boils at a much higher temp when it's under high pressure, also.

Why do you want to change things when your system is working perfect?

From your description it sounds like your heat gauge is reading high. It might be an idea to replace it, if it bothers you.

Other than that I don't see what the problem is?

I'm not looking to change it. I'm just trying to find out what the correct operating temp is for this car so i can see if it to high, too low or perfect.

I think the thread kinda drifted away from that somewhere along.

- Mark

Yes, we tend to Drift-off Very Often.
ZZZZZZZZZZZZZZZZZZZZZZZZZZZ Oops, I did it again

I don't think you have a temp problem. With that low pressure cap installed and if it's Not boiling out past the cap, then it's cool enough.
'Cool Man Cool'

Thanks Rick. After reading all the comments I believe the engine is doing just fine. Having spent a year rebuilding it, I'm just a bit nervous ;-)

- Mark

If, after doing an engine rebuild, you do not recore, rod or otherwise restore a radiator to "as new" condition, it's quite normal for an engine to run hot and the explanation is quite obvious. As an older engine accumulates miles, it looses some of it's original friction from tight clearances and thus produces less heat that when new. At the same time the cooling system gradually looses efficiency from scale accumulation in the radiator and other reasons. But when the engine is rebuilt all the new friction is restored but with a less-capable cooling system, thus the tendency to run hotter.

I'm not saying your engine is running excessively hot, but it is running hotter than the thermostat setting. If you live/drive in a hot climate, I'd consider replacing the thermostat with the factory-recommended 160 degree unit. If you live/drive in a cooler climate were summertime temperatures are less severe, I'd leave it alone and in time with accumulated mileage, it should run a bit cooler.

I don't think that at the 200 degree temperatures you've measured there really is any reason for undue concern unless the car is placed in a stressful situation (parade, traffic jam, etc.) on a blistering hot day.

G'day all, If you have just completed a long trip in hot ( 100F ambient) and you enter traffic, your temp gauge wil rise as the stored heat in your engine reflects on the water temp. If you are concerned, I suggest that at the first few sets of lights you shift to Neutral ( column or Auto) and raise the idle revs to draw more air through the radiator and circulate the water more efficiently. I am only talking about a few hundred more revs. An idling motor only generates a few horsepower and has the capacity to cool a few hundred. If the temp appears to get worse I would seek some advice from a radiator specialist, being careful of the "She's a new $850 radiator job for sure prognosis!" Best regards Peter Toet

I would do a simple test of the radiator cap. Take it to a shop that has a cap tester to verify that it is holding at 7 pounds. I have had new caps either defective of weak that had me crazy trying to diagnose things. If your cap is possibly opening at 4 or 5 pounds your temperature will slightly rise up somewhat.

You state that you need 3 gaskets to seal the cap to the radiator and this could also possibly lead to a pressure decrease if the cap isn’t holding to 7 pounds. Checking or changing the cap is cheap, easy and many times overlooked.

Hi Ron, Thx for the advise. Today I took the car to the guy that did the new core on the rad in July and he tested my cap. Not quite 5 lbs.

He's offered to modify the neck of the rad to fit an off the shelf rad cap, or make me a rad cap that will fit.

I asked for a quote on both options.

- Mark