460 Cooling Question

[lastdime]

I have a 460 SCJ that is finally cooling properly. It has taken awhile but after burping the system and adding a recovery tank there are no pressure leaks. I was able to run it at idle for 30 mins on a 95 degree day with no problem. Toward the end it got up to 98 degrees Celsius (208 F). 50/50 coolant under pressure has a boiling point of 124 C (256 F). I certainly don't want to reach the boiling point, but what should be the high temperature range on a 95-100 degree day?

Looking at a number of sources (mainly truck engines) the running temperature suggested is all over the board. What say ye FFR experts?

[Hoooper]

What temperature is your thermostat? And does it actually stop at 208F after 30 minutes or if you let it idle longer would it keep going up?

[Big Blocker]

Always been of the mind set that if the radiator is big enough to handle the engine under load, then the thermostat should maintain that temp . . .

When I built my MK-II, I installed a rad rated at 450 HP, car had a 325 HP 5.0 (302) T-stat set at factory EFI value of 192° F and never saw the gauge get beyond 90° C. Living in Las Vegas, cooling was a (serious) priority. I could drive all the way to Huntington Beach Ca. with my fan off . . . sitting in traffic here in Vegas, fan was on but still nothing above 90° C.
A lot of guys out there are pushing 500 HP and have cooling issues because the radiator is undersized for their anticipated HP.

Doc

[lastdime]

What temperature is your thermostat? And does it actually stop at 208F after 30 minutes or if you let it idle longer would it keep going up?

It took the full 30 minutes for it to get to 208 F. It was there for the last 10 minutes, I would say. If I had kept it going longer, it may have gone higher.

[lastdime]

Always been of the mind set that if the radiator is big enough to handle the engine under load, then the thermostat should maintain that temp . . .

When I built my MK-II, I installed a rad rated at 450 HP, car had a 325 HP 5.0 (302) T-stat set at factory EFI value of 192° F and never saw the gauge get beyond 90° C. Living in Las Vegas, cooling was a (serious) priority. I could drive all the way to Huntington Beach Ca. with my fan off . . . sitting in traffic here in Vegas, fan was on but still nothing above 90° C.
A lot of guys out there are pushing 500 HP and have cooling issues because the radiator is undersized for their anticipated HP.

Doc

I going to have to do more testing. Just wanted to know what you guys have experienced or suggest what the range should be.

[Hoooper]

I would note that idle isnt really much of a stress test, assuming your fan is working properly it shouldnt have any trouble cooling a really big motor at idle. Going to have to take it out for a cruise to find out. I certainly wouldnt have any issue with it maintaining 208 if the stat is something like 200F but if its a 180F stat and the fan is on all the time I would think youre going to be short on cooling once you start driving around.

My experience is probably not relevant due to different setups but I have a 190F thermostat, it idles and drives around most of the time at 193. It can get up to 199 on the highway but thats about it and is influenced by low RPM, holding 5th gear instead of 6th drops it to 193 pretty quickly. Its an FFR sized universal griffin 400-600hp radiator cooling a fairly spicy 376.

[NAZ]

If all you want is a ball park running temp as a measure of goodness, then your radiator cap pressure rating and your coolant boiling point will give you a NTE temp value. And for a running range you want to keep the water temp high enough to encourage fuel vaporization in the intake manifold and the oil temp where it will encourage evaporation of water condensation (a by-product of combustion and a constituent of blow-by). These are things that are of value to a street car. Also, be advised that a t-stat rating is the temp that it starts to open, not the temp it maintains. WFO will be higher than the rating on the cap, so consider the cap rating as the low end of the normal operating temp. More info here: https://www.stant.com/index.php/english/products/consumer-products/thermostats/abcs-thermostats/


If you want to put your engineering hat on and calculate running temp, then get ready for a lot of work involving thermal dynamics theory and math. And still, you will have to do a bunch of testing to nail down the real number.


I suggest you simply do everything practical to maximize the efficiency of your cooling system. That will keep you busy, especially if you’re not up to date on the tricks of the trade and need to research how to make your cooling system more effective. All car builders and tuners should acquaint themselves with how cooling systems work, it’s an important topic. If you need a good start on this, click on this link but don’t stop there – there’s much to learn and many myths to bust: https://www.stewartcomponents.com/index.php?route=information/information&information_id=14

[Purple Venom]

Have ran mine for 15 years on street and track, and my high temp has been up to 110 C (230 F). A typical temp on a day that you say, 95 degrees, I run around 95 - 100 C.

As mentioned above, have a big enough radiator and enough air movement. I have a 3250CFM puller fan (enough to blow leaves off my drive behind the car :D) HTH

Tim

[lastdime]

If all you want is a ball park running temp as a measure of goodness, then your radiator cap pressure rating and your coolant boiling point will give you a NTE temp value. And for a running range you want to keep the water temp high enough to encourage fuel vaporization in the intake manifold and the oil temp where it will encourage evaporation of water condensation (a by-product of combustion and a constituent of blow-by). These are things that are of value to a street car. Also, be advised that a t-stat rating is the temp that it starts to open, not the temp it maintains. WFO will be higher than the rating on the cap, so consider the cap rating as the low end of the normal operating temp. More info here: https://www.stant.com/index.php/english/products/consumer-products/thermostats/abcs-thermostats/


If you want to put your engineering hat on and calculate running temp, then get ready for a lot of work involving thermal dynamics theory and math. And still, you will have to do a bunch of testing to nail down the real number.


I suggest you simply do everything practical to maximize the efficiency of your cooling system. That will keep you busy, especially if you’re not up to date on the tricks of the trade and need to research how to make your cooling system more effective. All car builders and tuners should acquaint themselves with how cooling systems work, it’s an important topic. If you need a good start on this, click on this link but don’t stop there – there’s much to learn and many myths to bust: https://www.stewartcomponents.com/index.php?route=information/information&information_id=14

Thanks again NAZ. Once again you have provided me with some very crucial information.

[lastdime]

It's time for True Confessions. After making the latest improvements to my cooling system, including a fan shroud, I have no problems at all keeping the temperature around 90 C on the road or around town. However, when travelling at very slow speeds (10-20 mph) on a hot day in traffic, it can get up to 100-103 C. That hasn't been a concern. But, I've been asked to drive a dignitary in my Cobra for a city parade. It is only 1.6 miles long but will probably average about 5 mph. That should take about 30 minutes. Thus the idling test for 30 minutes. That's what this is all about.

[CraigS]

Making this simple. Most run a 180F T-stat so the normal running temp will be 180-190. Personally I am OK w/ getting to a max of 210. But I don't want it to stay there and I will drive easy until it drops. One thing I have found is I like to use the manual switch for the fan. When I see I am getting into traffic I flip the switch. I have found it easier to keep the engine at 190 by flipping the switch than it is to get it to cool back down if I wait too long. Most all cars will get hot until the fan kicks on and then drop back but, since daily driver temp gauges are heavily dampened, we don't see that happening. W/ the real temp gauges in our FFRs we see it, and while I realize it isn't an actual problem, I like mine to stay at 185-190 rather than cycling to 200-205, fan on, dropping to 185.