[Formulajones]

Doubtfull. I have our 69Z idling around 1100 rpm (manual trans) and daily drive it that way. It doesn't care as far as engine temps go, I mainly have it idling that high to help the engine produce a bit more vacuum for the brakes since we are up at 5000 ft elevation.

The biggest affect on idle temps I've found is whether you have vacuum advance hooked up to a ported source or manifold vacuum. Manifold vacuum, with the advance working at idle, has had a much more noticeable difference on engine temps, running cooler, in that configuration.

The trick though is having that vacuum advance dialed in so it's working at around 6 inches of vacuum and all in by 10 inches or so, and only adding about 10-12 degrees. I modify them to do so. If you run a can that adds 20 degrees and doesn't start working until 12 inches of vacuum it's not going to do anything for you at idle when hooked to manifold vacuum.

[Steve C.]

Can we presume the fans have proper shrouding so they pull air thru the entire radiator ?

Examples:

http://www.rondavisradiators.com/ass..._COPYRIGHT.gif

https://www.becool.com/sites/default...ts/82168_0.jpg


.

[i82much]

Originally Posted by Steve C.

Can we presume the fans have proper shrouding so they pull air thru the entire radiator ?

Examples:

http://www.rondavisradiators.com/ass..._COPYRIGHT.gif

https://www.becool.com/sites/default...ts/82168_0.jpg


.

yes these are Flex a Lite dual fans with a reasonably well-sealed shroud.

I don't think the temps are overly concerning.

https://knowhow.napaonline.com/tempe...ps-and-tricks/

"For example, a 180 degree thermostat begins to open within three degrees of 180, so 177 to 183. By 200 degrees, the thermostat is fully opened. The operation of the thermostat, open to close, is a range of about 20 degrees, so with different temp ratings, you can fine-tune the run temp of your vehicle."

So if my gauge is just a little off and reads 205, maybe that means the temps are fully controlled and the thermostat is just fully open at that temp.

I like having some heat since I drive on cooler days frequently and it also seems to keep the oil a little cleaner to run a warmer thermostat, but it would be interesting to see if I tried a 160 whether it ran any cooler or still floated up to 205 or so.

[Formulajones]

Originally Posted by i82much

yes these are Flex a Lite dual fans with a reasonably well-sealed shroud.

I don't think the temps are overly concerning.

https://knowhow.napaonline.com/tempe...ps-and-tricks/

"For example, a 180 degree thermostat begins to open within three degrees of 180, so 177 to 183. By 200 degrees, the thermostat is fully opened. The operation of the thermostat, open to close, is a range of about 20 degrees, so with different temp ratings, you can fine-tune the run temp of your vehicle."

So if my gauge is just a little off and reads 205, maybe that means the temps are fully controlled and the thermostat is just fully open at that temp.

I like having some heat since I drive on cooler days frequently and it also seems to keep the oil a little cleaner to run a warmer thermostat, but it would be interesting to see if I tried a 160 whether it ran any cooler or still floated up to 205 or so.

Cooler thermostat likely won't do anything for you. If it's running 205 with a 185 stat, it'll run 205 with a 160 stat.

Technically, if the cooling system is up to par, the engine tune is good, and the engine vitals are healthy, it should run right at the thermostat rating most all the time. If there is a deficiency somewhere in the mix then they will tend to run hotter than the thermostat rating. All the thermostat does is make sure the engine runs at least that hot and not colder than it's rated at, but nothing about the stat keeps the engine from getting hotter. That gets into either radiator efficiency, cooling fan efficiency, or engine tune, or engine being healthy and happy, or even engine components happy that play well with each other, (ie: meaning camshaft and compression are a good match for instance) Not saying this is your case, but when you have an engine that isn't very efficient with mismatched parts, it's much more of a struggle to get that combo to run cooler.

[Formulajones]

To help explain that further, using dad's car as an example.

I run a 160 stat in it, but as I mentioned, during our summer months when it's 100+ degrees, the car typically runs 175-ish. It pretty much just stays in that area cruising on the highway. It actually cools down a few degrees as soon as you take an exit and putt around 30-35 mph on back roads.

All that means is that the current radiator and shroud setup, and the current engine combo, that's about as cool as I can get the engine to run on hot days. That's all the system is capable of. When it's hot outside, it's just not going to run at the 160 stat rating.

Now on cooler days below 80 degrees or so, it's not uncommon to see it stick right around 160. It can sometimes see 157-158 as the thermostat just cracks open, and will fluctuate right there. That's the thermostat now doing it's job making sure the engine stays at that temperature. It can get hotter, but it won't get colder.

Now if I put a 180 stat in it, it would no longer run 175 on the hot days obviously, the thermostat would force the engine to run at least 180, and since I know the cooling system is capable of keeping it colder than that I suspect it would stay right at the thermostat rating. Slowing down on the backroads wouldn't cool the engine down any further either, as that thermostat would force it to run there.