coolant length of stay...

[pontiacgp]

I once had a 1967 Firebird parts car. It was used as an undercover car by the NYPD. It was ordered with the 400 HO engine, Borg Warner HD 3 speed manual trans, manual steering, no radio, just heat. Bare bones. It had only one fan belt and the single groove water pump pulley was huge like a pie plate. I figured they wanted to slow the water pump and alternator since it would be driven hard. It kept the 400 cool. I still have the HO exhaust manifolds and some other parts.

I wasn't aware of a 400 HO, all I have heard of in 67 is the 400 and the ram air 400....did the cops get something special?... 🤔

 

[bracketchev1221]

Thermostats were only used to get the engine to heat up quickly to reduce emissions and reach operating temperatures. The main thing is radiator surface area and heat transfer coefficients of the radiator material, like copper or aluminum. If you can increase the surface area of the radiator, you'll reject more heat. Thickness by itself will not do this. It won't hurt, but it won't necessarily help. This is why some 3 core staggered cores cool better than 4 core inline cores.

You want the pump to speed up for maximum cooling. Never slow it down. When dealing with radiators, you want turbulent flows and when you slow flow down, you can lose turbulent flow. The mass flow rate equation proves this to be true. Same with the air flow side. So make sure you trap the air to go through the radiator and not around it. Make sure all the seals are in place and shroud if applicable. Push/pull electric fans with suitable air movement will do the job or make sure your fan clutch, if used, is in good operating condition.

180 or 195 is perfectly fine. 195 was used in most CCC types so as to get that cat hot quick and stay hot enough to reduce emissions without burning sh*t up. But as noted, once the T-stat opens, it's going to pretty much act more as an orifice.

All that to say.....your radiator configuration and air flow across it will determine how fast you reject heat, not the T-stat.

This is the answer. TURBULENT flow cools better not stagnant water sitting in the radiator. Water cools by contact with the radiator surface. This is called the boundary layer of the water. You have to keep changing that boundary layer so a new surface of water touches the radiator surface. Leave the 180 thermostat in it.

 

[pontiacgp]

You don’t want it flowing too fast, such as with no t stat at all. You need the coolant to stay in the radiator long enough to let the air flow over it to do its job. No t stat can lead to overheating on hot days.

we used a plate with a hole in it to slow the flow down in our circle track cars, never wanted a problem of a stuck thermostat

 

[olds307 and 403]

Oldsmobile's heavy duty cooling option was a very big crank pulley and closed impeller water pump with a 4 core rad and 6 or 7 blade fan with a heavy duty clutch and shroud. Either A/C or deep gears automatically added the option. You want max flow without cavitation. The only reason to slow down flow is cavitation, not holding it in the rad. I ran cooler especially at lower temperatures with no thermostat. The only thing a thermostat does is regulate what temp the motor must get to. The only time I ran hot without a thermostat, same reason as with, the Champion 3 core wasn't large enough to cool my 403. Tell me why my underdrive pulleys caused my car to run hotter? They held the coolant in the rad longer. What are your current temps? I ran 195 to 210 with a 195 thermostat. The last trip I ran 165 to 180 with a 180 thermostat. Both high flow, because I want more flow with temp regulation. Between going from 5W30 to 20W50 and dropping my temps, I gained 8 psi oil pressure at cruising speeds. Also manufactures increased pressure to raise the boiling point. The only reason I use a 7 pound cap is if I have leaks and higher pressure makes it worse.

 

[69hurstolds]

Hmmm. Lemme just toss this out there....and by all means, feel free to change my mind.

Mass flow rate, aka "M dot" is KING in your cooling system. NOT residence time in the radiator. Period. The more mass flow rate you can achieve (within reason, of course) in a closed coolant system, the more heat is transferred. PERIOD. Science proves this. The problem with too fast of a flow is the surface areas are too rough and way too much turbulence is present that it becomes a flow hinderance, plus erosion becomes your enemy, along with pump cavitation risk. The reason they put the anti-collapse spring in the lower hose to the pump.

The reason that residence time in the radiator is BS is that in your car's coolant system, what goes IN must come OUT. It's a closed system. Or it should be. Part of the ability to run higher temps without boiling over is the pressure in the system. The coolant boiling point is raised by essentially 2 things in your car's system...anti-freeze and higher operating pressure. Anyway, I digress. So, if you're somehow able to increase residence time of the coolant in your radiator, what are you doing to the coolant in the block, or the heat source? The same thing. So your efforts to increase cooling via residence time is mooted because now your engine is pumping more heat into the coolant. To me, that just doesn't make sense.

Engines NEED to be at operating temperature to do their job efficiently. And peak efficiency gives you peak power. So you can rip those tires off the rims. Unless you have a stock 307... You get more wear if you're taking forever to warm up, like not having a thermostat, and if you rely on a carburetor, you need some heat to help with vaporizing that gas that you're dumping into the top of the intake (that's what the little exhaust heat crossover was designed to do). And then at higher speeds, you spin the pump faster, and then without that T-stat, or orifice plate, you start cavitating the pump because the pressure imbalance in the system. So it needs some backpressure in the block to minimize cavitation. Or you can slow the pump down with a bigger pulley. Clearances for piston to wall clearances, rings, etc., are blueprinted at engine build to ensure they can be at the right place when the engine is at full operating temperatures. And the T-stat helps do that quicker. Once it's open, it's just a pressure regulator for the water pump.

And if you STILL don't believe faster is better than slower in coolant flow, explain how, say, a factory-stock 1969 Hurst/Olds sitting in traffic would react to overheating conditions? It speeds up coolant flow via raising engine RPM. If you look at the front passenger side of the engine, you'll see a 3 port TVS. From that, you have the 3 ports- one to the distributor vacuum can, one to PORTED vacuum on the carb, and one directly to the intake manifold on a fitting just in front of the carb for full vacuum. During normal conditions, the distributor vacuum canister gets vacuum from ported source on the carb. As soon as the TVS senses an overheat condition (I forget the actual temp that happens) the core in the TVS moves to shift the vacuum to the distributor over to FULL manifold vacuum and blocks off the PORTED port. At idle, the canister normally wouldn't be activated. But with full vacuum, it is. 16 degrees of advance just like that. What happens? Engine speed increases, which increased pump speed and coolant flow. And since the fan is on the water pump, it spins the fan faster, too, increasing air flow. So air flow and coolant flow go up, thus Q dot, or thermal transfer rate, goes up as well. Assuming this brings temps back down to below the TVS setpoint, it resets and puts the distributor back on PORTED vacuum. Crude system, but that's why that TVS is there.

 

[olds307 and 403]

I see your point on cavitation and rough surfaces. I believe that is also the reason for the closed impeller water pumps with tighter clearances. More flow with less cavitation than an open impeller. The original Flowkooler plate riveted on the open impeller GMB did nothing to help any of my Olds cool any better. I would think the restrictor is more necessary with high rpm applications, it will only flow so much at 2000 rpm.

 

[Turbolq4]

Tstat also helps to avoid a laminar flow by introducing turbulence. Which increases heat transfer from the coolant to whatever it happens to be in contact with.

I'll save the highest power comes from highest efficiency dispute for later.

 

[Streetbu]

I'll jump in here. I had an issue with my car running hot for several years. Went round and round trying different things to solve the problem. Long story short, I had installed aftermarket aluminum pulleys to dress the engine up. They were a different size and in process, they slowed the water pump down causing lack of coolant flow and my over temp issues. A simple pulley change back to stock sizes and the problem was remedied.

 

[08Malibu]

Oldsmobile's heavy duty cooling option was a very big crank pulley and closed impeller water pump with a 4 core rad and 6 or 7 blade fan with a heavy duty clutch and shroud. Either A/C or deep gears automatically added the option. You want max flow without cavitation. The only reason to slow down flow is cavitation, not holding it in the rad. I ran cooler especially at lower temperatures with no thermostat. The only thing a thermostat does is regulate what temp the motor must get to. The only time I ran hot without a thermostat, same reason as with, the Champion 3 core wasn't large enough to cool my 403. Tell me why my underdrive pulleys caused my car to run hotter? They held the coolant in the rad longer. What are your current temps? I ran 195 to 210 with a 195 thermostat. The last trip I ran 165 to 180 with a 180 thermostat. Both high flow, because I want more flow with temp regulation. Between going from 5W30 to 20W50 and dropping my temps, I gained 8 psi oil pressure at cruising speeds. Also manufactures increased pressure to raise the boiling point. The only reason I use a 7 pound cap is if I have leaks and higher pressure makes it worse.

if your water pump was spinning slower, so was your mechanical fan. That would cause you to run hotter. Best bet would be to run a t stat and a thermostatically controlled cooling fan.

 

[olds307 and 403]

if your water pump was spinning slower, so was your mechanical fan. That would cause you to run hotter. Best bet would be to run a t stat and a thermostatically controlled cooling fan.

Also ran with Dodge Stratus electric fans.