Drilling the thermostat??

[undy]

Originally Posted by Bob In Ct

Holes in thermostats are not there to replace the bypass, but rather to let any air trapped in the top of the water jacket escape. Coolant that leaves via the thermostat heads back to the radiator and is replaced by cold coolant. Water entering the engine via the bypass is warmer and allows the block to attain a more consistent temperature.

Just my $0.02

Bob

You're somewhat correct.. except:

Water doesn't enter the engine via the bypass, it leaves the engine. The thermostat IN ADDITION to venting entrapped air/steam pockets can do double duty. It can TOTALLY provide the required engine coolant flow movement through the engine when the coolant bypass is done away with. This coolant flow through the bypass has nothing to do with attaining a more consistent temperature as its designed use is solely for a quicker engine warm-up (that amount of coolant bypasses the radiator). If you size and have the required amount of holes in the thermostat in conjunction with a blocked bypass then all that water that bypasses the radiator now flows though it. That gives you a "tad" more cooling capacity, which is valued to many big block, large cubic inch Cobra owners. The minus part of the equation is that engine warm-up suffers somewhat, not a big deal with me. The big thing you've got to worry about is too many and too large holes. Then the engine, on cooler days, may not come up to temperature.. Not a good thing.


BTW.. The cross-sectional area of a 1/2" (ID) coolant bypass hose and 4ea 1/4" drilled holes is the same, down to a hundredth of a square inch.. Flow should be approximately the same, save some unknown variables.


Dave