Why Drill Holes in your Thermostat?
The main reason to drill a hole in your thermostat is to keep your car cooler by controlling the KR. However, these holes only reduce the overall engine temperature by about 5 degrees. Did you know there is a much more important reason for doing this?
While at the track you open the hood, maybe ice the charger, and let the motor cool down between runs. This may bring your coolant temps down to very low levels, which is good. However, these cool temps may actually slow you down. With the coolant and engine cooled down, there is no coolant circulating until the engine temps reach the temp of the Thermostat.
This would normally be OK except when you’re racing the combustion chambers heat up very quickly. This means the coolant around the cylinders and heads might reach 250 degrees before the stat even begins to open. This isn’t ideal, because it can cause high levels of KR in the back half of the ¼ mile. You can eliminate this problem by drilling holes in the thermostat to allow a small amount of coolant to consistently flow.
“Performance blasting down the ¼ mile isn’t the only advantage of having holes drilled in your thermostat. If you live in a colder climate this $11 investment might just save your cylinder heads from being cracked and damaged due to dives in coolant temperatures as your winter chilled radiator dumps it’s freezing coolant through your heads.
A drilled stat would be much more forgiving by providing a continuous flow of coolant and reducing sudden and drastic temperature changes.”
– Andy H
1999 Grand Prix GTP