Why Drill Holes in Your Thermostat?
I guess the obvious reason is to keep your car cooler therefore controlling KR. However the holes only reduce overall engine temps by about 5 degrees so we have a much more important reason for 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 however when you're racing the combustion chambers heat up very quickly. So the coolant around the cylinders and heads might reach 250 degrees before the stat even begins to open. This is very bad and can cause high levels of KR in the back half of the ¼ mile. By drilling the holes in the thermostat you can eliminate this problem because you will always have a small amount of coolant flowing.
This is from ZZPerformance.com
They recomend a 180* t-stat for your L36 motor...and this is the reason why you run a cooler, or sooner opening tstat with holes in it.
In the red circle is a crack in the cylinder head.