Anyone ever drill holes
in the thermostat to help
with the filling of the rad
to get rid of the air

It does help.

What I would suggest as a more perminant solution, would be to installa bleed screw in the goose neck.

I drilled two small holes in mine to assist with that. What Andy suggested above is a good option, too.

Matthew

Drilling the T-stat is super easy and fast when installing a new T-stat. A single 1/8" hole is usually what I perform or suggest.

Yeah, don't get carried away, especially if you live in a cold climate. A single 1/8" hole is plenty.

I've never drilled mine, if you burp the system properly on the initial fill, have a working radiator cap and don't let the overflow ever dry up, air will never get into the system.

Some OEM stats come with a tiny hole in them and a little check valve on it.

I am using a thermostat made by Stewart (got it from Summit). It is a high-flow unit with the holes already drilled.

I tried one of those... It had 3 big holes drilled in it. Hope you have better luck with it.

The car wouldn't get over 140F in cold weather so I took it out. Heater wouldn't work and the 4+3 won't even shift into overdrive if the car isn't warmed up enough.

So far, the thermostat is working great. The car does run a little cooler, but for my driving style and use, it does the job. Most of my driving is in the Smokey Mountains - steep hills, hard curves, long stretches of uphill and downhill runs, etc, and depending on traffic, quite a bit of time just setting. Anyway, I'm happy with the unit. May not work for everyone.

I've used Stewarts in some of rhe racecars, like em'.

Yeah, but race cars don't get driven to the grocery store on a 30F morning. And if your chrome bumper doesn't either, then I can't complain.

I think they say the holes help flow, but honestly, the stat while open has way way more open area than the holes, so I'm not really convinced there's a significant benefit.

I don't see no chrome bumpers on your car, guess you need the heat though.

I put the Stewarts in to help reduce the air in the system, it's a problem on soe of the cars, there's even a petcock on top of the radiator to bleed air. Th Sterarts seemed to help some.

High Performance Thermostats

Manufactured by Robert Shaw and modified by Stewart, these custom thermostats feature a balanced sleeve design and are constructed for high flow, high RPM applications. Strongly recommended for any performance application - must be used with Stewart Stage 2, 3 or 4 water pumps. Our Stage 2,3 and 4 Small Block Chevy water pumps do not have the factory bypass hole, therefore we put three 3/16” hole in our modified high flow thermostats, this moves the bypass to thermostat. This also allows air to escape on initial system fill making bleeding the cooling system much easier.

May just be advertising BS from their website but the air bleed does work.

I have a Stewart stage 1 pump. They recommend their drilled stat even for that.

Also on their website:
Stewart further modifies its thermostat by machining three 3/16" bypass holes directly in the poppet valve, which allows some coolant to bypass the thermostat even when closed. This modification does result in the engine taking slightly longer to reach operating temperature in cold weather, but it allows the thermostat to function properly when using a high flow water pump at high engine RPM.

First off, the heater piping, at least on mine, also functions as a bypass.

And their statement about "slightly longer" is complete B.S. If it's cold outside and you're on the highway, your car will never reach operating temperature. With a non-drilled 180 stat, your car will reach 180F under almost any outdoor conditions.

Normally, on a cold day the engine will heat up enough to crack the thermostat, then the cold water from the radiator will easily cool it back down and shut the stat. But a drilled stat will always be cooling the engine, so it will never be able to heat up enough to crack the thermostat open. Three 3/16" holes probably allow enough flow to keep the engine operate at 140-150F.

Also if you understand coil characteristic curves, a radiator with only 5% of its flow can still put out 25% of its cooling capacity. This relates to the coil's efficiency and also explains why increasing flow to 110% doesn't always help much.



Stewart's holes are drilled to achieve whatever minimum flow they deemed necessary at high rpms to prevent blowing gaskets or cavitating the coolant in the pump impeller. The air removal is just a side effect, and could be accomplished by much less, like a 1/8" hole, or better yet, the little air release valves used on oem thermostats which don't allow any water to flow at all.

I agree, and as I said before, a single 1/8" hole drilled into the brim of a stock T-stat is all you really need.

I just put one in yesterday 180 degree. Car now runs at 179 to 181 degres without air on and 189 to 192 with air running. I have not been in heavy stop and go traffic yet so no info on that. I live in South Georgia and weather has been at 100 and more for a couple of weeks. This is a reduction of 10 to 15 degrees and oil temp is also lowered by the same amount. I am pleased with it. I work on motorcycle so I am used to burping cooling systems to get air out. Keep the tank to required level and be certain radiator cap is correct and working properly and it will take care of itsef after initial burping. This is my secong 1989 Vette and I had the same results from previous one.

Quote:
What's the best way to burp to get the air out

Quote:

Take the rad cap off before you start the car and let it idle until it warms up enough to open the thermostat. You'll see the coolant level in the radiator drop, then add more until full. Put cap back on, repeat process later. Takes a couple times.