old and new Thermostat tests with questions

[John Kelly]

I decided to replace my thermostat, bought a new one (on the right in the pictures) but did not have the gasket sealer. So, to fill my time I decided to see how well the old thermostat operated compared to the new by placing them both in a pot of 188 degree (see pic) water. The old thermostat opened quickly, the new did not begin to move until 220 degrees (est. see pic), and really opened at 225 (est. see pic) degrees.
As often, online information lacks specifics when you compare different sources and what I found for the normal operating temp for a 1967 440 is an operating range of 175 degrees to 235 degrees. My questions are these: 1. Is the old thermostat opening quickly because it's old and worn out? 2. Is the new thermostat, opening at about 220 degrees, functioning correctly (NOTE: the parts guy at O'Reilly's said it's a 180-degree thermostat.)? 3. At what temp should a proper thermostat open for this 440?

 

[saforwardlook]

It seems to me that waiting until the coolant temperature reaches 220F is waiting too long. Maybe on newer models that might be acceptable, on our older vehicles it seems too delayed.

It also seems that everyone supplying thermostats these days such as Stant or others are actually selling thermostats built in China by a company called Moto Rad. That brand claims they have advanced technology to prevent a car from overheating.

I recently ordered a thermostat from Stant and when I opened the box it was also made by Moto Rad as stamped on the part.

One of my friends trains doctors to use a new synthetic skin material to help burn victims heal more quickly than the old technology that relies on the use of cadaver skin to cover the wound and help it grow back to healthy skin. As such the company provides him with a vehicle of his choice to travel all over the country to train doctors in how to use the new product. As such they provided him with a new Jeep Grand Cherokee with the Hemi engine and German ZF transmission and in two years he put over 90K miles on that Jeep. As many with Hemi engines have learned, just before hitting 100K miles those engines have failing roller rocker lifters and his was no exception. Since he also ordered the extended warranty, the dealer covered it under warranty and when he was talking with the tech that was replacing the cam and roller lifters he noted that the tech replaced the original thermostat at the same time with a thermostat in a Chrysler Branded box - he noted that it too was a Moto-Rad brand. Recently I ordered a Stant 180F thermostat and when I got the box, it too was labeled Moto Rad. So all I can say is no matter what brand one buys, it is likely a Moto Rad.

I also noted that some members of the Chrysler 300 Club International, Inc also have used that brand thermostat and have noted that the opening temperature seems to deteriorate over time/mileage to opening too quickly before the engine is fully warm. So I don't know who or what to believe these days..............................

 

[CBODY67]

To me, the issue is not so much how quickly the thermostat opens, but the temperature that it does it at. Admittedly, a more gradual opening point would be preferred over a sudden-open thermostat to prevent "thermal shock" of the metal. BUT fully open at the rated temp.

Were these both 180* F units or was the later one 195*F rated?

Years ago, it seemed that we believed that the thermostat was fully open at the rated temperature. As it turns out, that spec temperature is when the valve STARTS to open rather than when it is fully open. As we notice when coolants starts to flow through the radiator at that rated temp, that does not mean "fully open" as we always suspected.

Just some thoughts,
CBODY67

 

[volksworld]

went through a similar deal while chasing an overheating problem on my 454 chevy camper....every FLAPS thermostat in a different box was a Motorad...I removed a good new one while troubleshooting and wound up installing a new defective one, the third one worked...boiled them together to find out...due to the size that was the only style available...in your case I'd look into a Robert Shaw style thermostat they have 3 posts supporting the center pin instead of 2...back in the day it was standard procedure to replace a part before it failed, now the odds are the new part will be worse than the old one...Stant closed up US (Arkansas)manufacturing in 2021 and did some sort of inventory deal with Motorad for whatever was left

 

[John Kelly]

The new thermostat is made in Israel by a company named Murry according to the box. It's rated at 195 degrees. The old one is rated at 160 degrees. I just found the ratings stamped on both thermostats. So now I need to figure out the ideal operating temp for a 440. As I mentioned, the internet ranges from 175 to 235 degrees. That seems too big of a spread to make a decision.

 

[CBODY67]

Forget "The Internet", what the cars came with was a 180*F thermostat. When emissions came to be a larger issue, then they went to 195*F thermostats, OEM. No difference for factory a/c cars or not.

To me, if someone perceives their engine will make more power with a 160*F thermostat, so be it, BUT that is a more specialized application where "coolness" is desired. Whereas a normal engine needs something warmer for decreased cyl wall wear and a heater that gets hotter quicker in the COLD times of the year.

In a Rochester Carburetor book by S-A Designs, it was noted that greatest power is really made with a warmer engine, which might extend up to the 235*F range. So "cold mixture" warmer cyl block?

The differences in how the two thermostats acted can be somewhat explained by their temp ratings, to me. Lower one "snapping" open as the other one was lazier.

To me, the "best" option can be something between 180*F and 195*F, unless you have a '55 Buick which still can tend to overheat with a factory 160*F thermostat. Cyl bore wear was not important on those Nailheads as they had higher-nickel content blocks and cyl heads.

In order to get a baseline for YOUR engine, start with the 180*F thermostat and go from there.

CBODY67

 

[71Polara383]

170-200 would be the range I expect to see. 210 wouldn't bother me idling in traffic on a hot summer day.

Anything beyond that - somethings wrong.

 

[Gerald Morris]

What year was your 440 built? I don't recommend 160 F thermostats eve here in southern AZ. I use a stock 180F open skirt RobertShaw thermostat during the summer, which is precisely what a 383 built in 1966 had. I now use a 195 F RobertShaw for the winter, as I observed that allows my engine and cooling system to reach the desired running temperature of ~195F I like, summer and winter. I would run the engine hotter if it had been built to sustain a somewhat higher temperature without degraded performance from pre-ignition, viscosity breakdown and such, as higher temperatures help bur off extraneous carbon, which we DO'T WANT DEPOSITED IN OUR BORES, and also better use of our fuel for the purpose of rolling rubber on the road. I've found 195-200F pretty optimal for keeping the oil reasonably viscous, not blowing any seals, yet boiling impurities out of my crankcase.

Flush "Motorad's" CRAP. They use coerced labor, as much as the chinese do, despite the supposition of being a "democracy."

Edelbrock high flow thermostats are STILL MADE IN THE U.S.A.! If you can't find any good RobertShaw thermostats, then go with Edelbrock. Mr. Gasket's line is made in Taiwan, but does OK, if not great. They IMITATE RobertShaw's drop-skirt form, but don't last too long. I tried one about 4 yrs ago.

Get the FSM for the exact year of your vehicle, and see what the factory spec temperature for it is. As a rule, pre-1972 stuff will be 180F, 1972 on 195F.