91z07

I've noticed people are drilling holes in thermostats. Can someone explain the need for this and specifics on how to do it? I'm planning on installing a 160 degree thermostat soon since I live in Texas and I don't drive much in winter. :confused:

CorvetteZ51Racer

If you're putting in a 160 degree stat, don't bother drilling. I honestly don't understand the point of drilling the T-stat anyway...just install a colder stat if you want to circulate water sooner.

65Z01

TPIS "Insider Hints" has this "trick" as a way to improve cooling.

They suggest plugging the normal stat bypass passage and drilling a set of holes in the stat, one set for summer and another for cold weather.

UDLUV12

91z07,

I'm telling you, this is one mod I will never be without.
I've got 4 .200 inch diameter holes drilled into the lip of my 160* thermostat.

I don't drive the car very much in the winter time...maybe 45*F or better days.

During the summer months this is where this mod pays off.
Prior to me installing the 160* thermostat with the 4 .200 diameter holes in them, my temp readings would be 211* to 214* during 95*F + days.

Once the new thermostat was installed my temps dropped amazingly to the 184* to 186* level.

No other changes made...other then the 4 drilled holes.

I'm the original owner of my Vette, and it has never run so 'cool' in all its life.

I think we all ought to be thankful to TPiS for sharing this easy to do mod with us. I know I am, and I'm sure there are a bunch of us on the forum who agree.

Good Luck with your decision.

CentralCoaster

Do some searches on this subject, and you'll see it has come up often.

Drilling the stat only really affects how long your coolant temp takes to warm up. Personally, I'd like the coolant to heat up as fast as possible to 180 or so and stay there. Engine doesn't run well when its too cold.

LT4BUD

I did this and I have mixed feelings on the results.

In cool or cold weather it greatly increases the time for the car to reach temperature and in cold weather it never reaches 160.

In warm weather the idea is to increase the flow so as to increase cooling. With my 160 stat the car would normally run about 173 on highway. After the I drilled the holes it did run a little cooler especially in 90 plus temperatures.

Having said all that, I would probably conclude that they didn't do all that much in warm weather & in cool weather the delay in warming up & low operating temps are bad. So my recommendation is don't do it on a street car.

jfb

The 160 thermostat will not allow your engine coolant to run cooler in summer temperatures, 85+ and probably lower. The C4 radiator was designed to operate at 180 or 195 F and that is one reason the factory thermostat is 180 or 195. Above about 162 F, your 160 stat is WIDE open and cannot control your coolant temp at all. Putting holes in the 160 stat merely allows more than normal coolant flow before it opens, increasing the time for the engine to get to operating temperature, BUT.... it will still go much higher than 160 F.
My 87 has always had a 195 stat and I installed a toggle sw to turn on the main fan when I know that the temp will soar, mainly at stoplights in the summer. Above 35 mph it would stay close to 195, at stoplights in 90 weather with the fan on it would go to 210/220 if I sat long enough and cool back to 195 when I got underway. Last year I installed a Stewart pump which has higher flow even at idle and last summer at stoplights with the fan on it would not go over 200 and would cool down much faster when I got underway. I knew the factory waterpump was inadequite because I could race the engine at a stoplight and the engine temp would fall.
A 160 stat does NOT stand over your engine and threaten to whip it if it goes over 160 and the factory radiator cannot get rid of heat fast enough to maintain 160 F coolant temps in 85+ temperatures, it wasn't designed to. If your 180 or 195 stat allows 200+ temperatures in the summer, then the 160 thermostat will do the EXACT same thing because both stats will be wide open and your cooling system temperature will settle where the radiator can get rid of heat as fast as the engine makes it.
In the winter at lower air temperatures, the radiator has much higher heat ridding capacity and the 160 stat will control the coolant to 160 degrees which is too low to operate an engine.
The ECM turns on the main fan at 228 F and the auxiliary fan at 238 F and GM says to shut the engine off when the coolant gets to 260 F. 238 F will do no harm to your engine and I believe that we are uncomfortable with 200+ temperatures because older cars we have owned would boil over at these temperatures and leave us sitting at the side of the road. I owned a 64, 69, and a 74 vette and drove them every day and I never saw the engine temp go above 180 F, but those cars were designed with larger radiators and could do this.
Its your car and if you want to install a 160 stat in it , go right ahead, but that thermostat will not keep your engine temperatures from soaring to 200+ in high summer temperatures and below 35 mph.

vader86

I wouldnt do it unless i had serious cooling problems. That includes a high power engine that likes to run hot and super hot climates.

TPiS apparently recommends it for their Miniram, i guess it had some cooling problems in testing.

I wouldnt drive in winter with it, theres no way that the engine will make it to closed loop. Your mileage will suck.

grapeknutz

The reason is to purge the air that is trapped behind the Thermostat I think the drill size is .060 or so one hole does it!

hookedup

:iagree: with grapeknutz, just makes burping the system easier.
I drilled all my thermos with a .125 bit, no more trapped air.

Good luck, Dave :thumbs:

CentralCoaster

Ahh.. good point. Now that I think of it, many of the factory thermostats have a little check valve for this purpose. (little hole with loose metal flap in it) The hole closes up when it sees flow from the water pump though.

chucks88

After the first 8 responses to this thread I was starting to think that I was the only one who did this to purge trapped air.

Corvette0096

:iagree:

87SAM

That was my thinking excatly! Never have a problem burping air out after radiator work. One 1/16" (or smaller) hole will do it.

Strick

Hey JFB,
You say you installed a Stewart pump. Was it a complete coolant pump electrically driven? And does anybody know if you can reprogram an ECM to have the fans come on at a lower temp?
Strick

mackeyred96

This is an old trick. We did it 30+ years ago before trick stats.

jfb

Strick, I own an 87 L98 and did some engine work last Spring and the GM waterpump had a wet weep hole, so since it was apart, I bought a Stewart mechanical water pump ($104 to my door) because I know I needed more coolant flow and it definetely keeps my engine cooler. I have the 195 thermostat also.

Strick

Hey JFB,
These electric water pumps for the LT-1 look exciting to me. You're from Cinncy, my son lives in Florence, oh well. Does your pump have a weep hole in it? I see you don't have Opti-Spark problems.
Strick :seeya

grapeknutz

Come to think of it.... it was 30 years ago that I learned about that trick! :lolg:

black bart

Robert Shaw thermostat has a air bleed valve built into it. :leaving: