Nathan Plemons

Seems to me that it would allow more coolant to flow through the thermostat, however it would allow the coolant to flow while the thermostat is closed as well. I guess the theory is that it will help out a little while the thermostat is open, but the holes will be so small that it won't hurt anything while closed. It's not like it's gonna keep that V-8 from warming up

I just installed a 160 thermostat, with the stock fans programmed to come on at 185 keeps it below 200 degrees 99% of the time.

No Go

Only reason I've heard for drilling holes into one's thermostat is to bleed air bubbles out of the system when starting the engine after doing coolant maintenance. Drilling more holes into the thermostat for increased cooling sounds bogus-like same reason people recommend removing the thermostat altogether in the older musclecars-it didn't work due to the coolant moving to quickly through the system!

Also my DRM 180 thermostat for my 96 was identical to the factory 180 thermostat except it had one hole drilled into the outer edge-I assumed to help with bleeding air bubbles-my car runs no different than before the change.

DoubleAught

Niagra, NY? I live in the south, and I drilled my stat. When it started getting cool, my car wouldn't get up to operating temp, resulting in reduced mileage. Ended up putting an undrilled one in for cooler weather.

jcazin

I drill the thermostat so, if it fails and closes shut, I don't melt down my engine- no other reason to do it.

tommelton

There can be one other reason to drill the thermostat. I have an 82 Vette with a very high-flow pump. If I allow the engine to warm up at idle, the thermostat will open normally. If I am at cruising speeds, the thermostat cannot open against the pressure from the high-flow waterpump. The only way to get the thermostat to open is to switch the temp lever from Cold to Hot to allow water to circulate through the heater, thus relieving the pressure and then it will open immediately.

Trust me, there can be valid reasons.

Tom Melton
82 CE
86 Z51 Coupe

torquejunky

For this mod to work you need to plug the bypass hole at the water pump. Just make a gasket for the water pump without the third hole on the passenger side. The bypass is normally needed to protect the pump by keeping some water moving in it when the thermostat is closed (it bypasses water from inlet to outlet of pump at the front of the block). If you drill holes in the thermostat the bypass isn't needed as you will always have some flow through the whole cooling system. What’s the benefit?

With the stock bypass configuration coolant sits in the engine when the thermostat is closed. Because the coolant isn't moving it can allow hot spots to develop. If the coolant is flowing then it will have a more uniform temperature. In addition to this the bypass will always short-circuit the cooling system somewhat even when the thermostat is open. By blocking the bypass all coolant has to flow through the engine and radiator. Don't ever block the bypass unless you have a thermostat with the holes drilled in it.

That's the theory, I've never tried it but TPIS says it really works. Keep that
86 cool :cool:

No Go

torquejunky: I haven't studied the coolant system on SBC in detail, but I was under the impression that coolant constantly moves throughout the water jackets of the engine but may or may not travel through the radiator depending on whether the thermostat is open on not. If in the stock configuration, coolant did not move then I would definitely think pockets of coolant would have a problem with boiling and air pockets such as in the cylinder heads.

Needing holes to reduce the pressure within the system is a new one on me. I would lean toward a weak thermostat or other abnormality within the system, but heh you learn something everyday.

87SAM

I drilled the 1/8" hole in my stat this spring and it work very well as far as being a breeze to purge the air out, BUT, I too have the problem with it not coming up to operating temp when its cooler outside (70) and running on the freeway. This fall I will install a undrilled stat or maybe try a 1/16" hole.

steve1ph

what i did was go down to the parts store and buy a 160 degree thermo for just a plain jane 350 chevy engine fits fine no holes needed for about 6 bucks. dont ask for the corvette thermo or you will get the power robbing hot one.