Years ago, I ran mainly Pontiacs, in A and B bodies, and so had some over temp problems, played with much stuff.....and so noticed one thing....the t-stats open at X Temp and they stay open pretty much, and so over the years I have noticed that the stats used to have openings of say 1.25" in diameter, never measured one so don't hold me to it....back then it was the size for any temp rating.....

then I was wondering why my Pontiac was running warmer....and noted the size of the opening in the stat....it was smaller than the other previous ones...flow restricted... so to drill 2-3 holes in the apron and that makes up for the restricted flow when open....

same thing for my modified '72 vette.......IF you can find some 160 stats on the shelves/racks you MAY find the open flow hole is larger in diameter that is the size what used to be years ago....

 

I first heard about the Thermostat 1/8" drill hole 25+ years ago for a fix for Jeep Cherokees jumping temperature needle.

When I drove the Cherokee [With a 180F thermostat] the temperature needle would sit at 180 for a while, then JUMP to 190 very quickly.
Then slowly drop back to 180f. The process would repeat about every 10 minutes.
It was very obvious the thermostat was Sticking and the Popping open at some temperature much higher than the 180 setting.
You see the thermostat door has to Open "INTO" the high-pressure hot-water steam.

The small pair of 1/8" holes drilled into the collar, make the valve open much easier and more gradually.

When the value is closed!
The holes allow the air building up on the hot side to go to the radiator [this is good]
Less air, means less potential air Insulation, blocking the water from coming in contact with the valve.
The small amount water transfer through the two holes, keeps both sides of the value a more constant temperature.
The equalized temperatures allows the valve to open gradually, based on temperate, rather than a Shock Open when it's very hot.
The holes help equalize the water pressure on both sides of the valve, which also allows the value to open easier.

For all of my cars ever since, I have always drilled a pair of 1/8" holes into the thermostat, even on my C4-95

 

The thread is over 8 years old.

 

Old thread, old myths.

 

That's a good idea but I just drill two 1/8 holes in mine. This allows the air to circulate before it opens but doesn't hurt cold start warmup.

 

So it's not relevant anymore?

 

I am so bored with covid-19, I cant believe I have read 8 years worth of threads.
I will try to be more aware of the thread dates.
However it still a good solution to reduce air-bubble build up and improve cooling.

 

No its not.

 

Well, I'm bored too, with this covid crap so I'll add my 2 cents to an old thread. I run a 160 degree stat and have for almost 50 years, now. I've never worried about slow warm up or overheating. If you're running your car in the warmer months when there's no snow or freezing temps, you shouldn't have to worry about slow warm-up. Every time there's a thread about thermostats and engine temps I roll my eyes and say "Here we go, again".
Duane