C1-Curt

I am installing a Dewitt radiator fan combo in my 1960 and I am trying to figure out which thermostat to run, a 160 or 180. The spec says the fans have a switch that turns them on at 195 and off at 175.

Which should I run and and the reasoning please?

Thanks,

Ironcross

180 is the best all around stat for early Vettes and the OE temperature...the 195 is for emission control for all engines if so equipped.....160 is not used except by some individuals that thinks a 160 is the answer to overheating....

jim lockwood

You should run a 160 t'stat if you have Rochester fuel injection on your engine. Otherwise, run what you like.

Jim

Ironcross

Not sure of that statement as my 62 has never over heated and still has the factory 180 stat....As for example with all the high 90-100+ temperatures the last few weeks it ran below 180 and normally its below 175 all over in any condition.....Nothing has been removed from its complete cooling system that includes the clutch fan, water pump, and those where ever shrouds as I don't know where they are that people say existed

MikeM

I agree with Jim's statement. Some areas of the country seem to have gasoline that doesn't like the higher temperatures with the Rochester FI. Early units FI units seem to like the higher temperatures even less than the later ones. But, you already know that, don't you?

I have little problem here in southern Indiana, maybe you get similar gasoline in Michigan?

To answer the OP's question, I don't see why the ON/OFF fan switch calibration has anything to do with what thermostat he uses.

Frankie the Fink

The T-stat controls the lowest temperature at which your radiator fluid begins to cool the engine. It is unrelated to overheating (unless it's stuck shut!). I run 160* in both of my classic Chevy's and use the safety T-stat (they are supposed to go to the full open position in the case of severe overheating). Some say your oil efficiency and combustion quality is diminished by the lower temp T-stat. I don't think these old Chevy's are that finicky and have NEVER had a problem with the 160*.

Here is the sticker on my '61 radiator and pretty much says it all.
And here is the temp my car runs at after an hour on the turnpike at 70MPH on a hot Florida day - right where I like it ! And yes my temp sending unit and gauge have been checked with an I/R gun and are spot on.

waltonb123

Under "normal" conditions it shouldn't matter. Most engines are running 185 to 200 so all your doing is opening up the flow earlier with the 160. Now with that being said, after I recently installed an aluminum radiator my car tends to run under 180. So I switched to a 160 so that I had full circulation at the lower temp. I think you will have the same situation with yours. More than likely your fans won't come on unless your running the a/c or under some extreme conditions so the thermostat shouldn't have any effect. If I'm wrong, someone will correct me.

65tripleblack

In the summer, most of the time the minimum temp the engine will run at is determined by the capacity of the radiator. On any day where the ambient temp is above about 85 degrees, the radiator is rejecting heat at its full capacity, so thermostat selection makes no difference. In other words, with a low temp thermostat, or even with NO thermostat, in ambient temps over about 85 degrees, the engine temp will stabilize based on it's load and the heat rejection cap. of the radiator.

If your radiator had the capacity to keep the engine temp at 160 degrees on a hot day of say, 95 degrees (which it doesn't), then in order to take advantage of a 160 degree thermostat, you'd have to reset your low-limit switch to 160 rather than 175, and reset the high-limit switch to 180 rather than 195.

MikeM

If your car has SUFFICIENT cooling system capacity, the thermostat will CONTROL both the upper/lower operating temperatures of your engine. Period! And I ain't gonna' argue about it!

On the other hand, most Corvettes I've seen and heard about will easily cool on the highway or at least above 30 mph or so unless the radiator is plugged. The 160* thermostat will still help by keeping the engine temp lower and when you pull off the road and stop, you'll have a lot less heat radiating into your fuel system to cause perk/vapor lock problems with your FI.

That's my story and I'm sticking to it.

Frankie the Fink

[QUOTE=MikeM;1581548938....and when you pull off the road and stop, you'll have a lot less heat radiating into your fuel system to cause perk/vapor lock problems with your FI.

That's my story and I'm sticking to it.[/QUOTE]
I don't want to argue either but help me out with the rationale on this last statement. The T-stat is wide open after a hot run and (to my thinking) the temp range of the T-stat is irrelevant.

wmf62

as you well know, the temp of the thermostat only determines the temp water starts circulating and tries to control the lowest temp on the fluid (keeps the engine/radiator from freezing up going down the road). once the stat opens the temp of the stat can/will do nada if the operating temp is above its rating.

Frankie the Fink

Which is the source of my inquiry back to MikeM. How does a lower T-stat temp help with heat/perc issues when pulling off the road after a hot run ? Pretty straightforward question I'm thinking

Not being a jerk - I'm hoping he's right and I'll feel even better about my 160* choice...

MikeM

The key words are "sufficient capacity". "Capacity" in this sense has nothing to do with additional outside influences like electric thermostatic controlled fans or clutch fans. Strictly heat rejection capability of the radiator.

The thermostat isn't always open "after a hot run". If the cooling system has the capacity to over cool the engine to a lower temperature than the thermostat calibration, the thermostat will start to close up in order to bring the temperature back up.

As an example: I had a '56 Chevy once. Had a 327 in it, stock V-8 radiator. Stock four blade fan. No thermostat. IR guns weren't invented yet but the engine always ran between 145-160 as I recall as registered on a good mechanical Stewart-Warner gauge. Didn't matter if it sat and idled all day or run on the road.

I put a 180* thermostat in it at a later date. It ran on 180* day in, day out. You can bet that termostat was cycling open/shut continuously to MAINTAIN that temperature.

Another example: Ever see a big diesel truck grossing 70+ thousand pounds running down the road with the shutters in the radiator completely closed to block off air flow? That is because the engine is overcooling and the shutters (thermostat) snap shut to pick up engine temperature.

Frankie the Fink

Hmmm.....I'll have to cogimitate on that some...

MikeM

..........and it also stops the coolant from circulating if the operating temperature starts dropping below the thermostat setting due to "sufficient cooling system capacity".

That will probably never happen on your old Corvette with your old original radiator or copper replacement still on board.

Some people want to believe that GM put just a big enough radiator in the cars to let the engine run "around" 180* and anytime there was an increased load on the engine or lessened air flow, the temperature was just expected to increase. This is hardly the case at all.

Every automotive cooling system has excess capacity designed into it. Every one that I know of. If you have excess capacity under any of your operating the conditions, that little thermostat will be cycling open/closed to maintain it's setting. Guaranteed!

If your heat load exceeds your cooling capacity, then yes, your thermostat will stay open. The point here is, running above 30 mph, you have little engine heat and lot's of airflow. This is when you can take advantage of the 160* thermostat, even in a Corvette with a less than legitimate cooling system.

Mike Ward

MikeM is right. Excess cooling capacity is not something that we often encounter on old Corvette though.

waltonb123

Which is what I was trying to say earlier (just not as eloquent as MikeM)!

toddalin

Or maybe a way to make a little more power, keep the engine a bit cooler, and avoid boil-over when you finally do have to stop and idle in traffic for a while.

Dyno testing continually shows that a colder engine makes more power as long as the temp is >~150*. I run a 160* in the '64 and the engine runs at ~165* on the road. If I pull up to a stop light and have to wait there, my engine temp starts climbing from 165*, and not 180*. It gives me more time before I have to worry about anything.

rustylugnuts

160* runs best in my fuelie here in the hot Tampa area.

rustylugnuts

65tripleblack

Exactly. And this situation is what I'm talking about with most older cars, including Corvettes older than 1984, in post #8. Newer cars have a lot of excess capacity designed into their radiators. In THAT case, the thermostat is cycling between wide open, and throttled, to modulate water flow in order to keep ENGINE temp within a tight range of its rated temperature.