by Dick Zakrzewski, Duane Davis
It isn't often that two widely diverse problems can be resolved with the same solution. What's even more unusual is that the solution is very simple and inexpensive. The first problem is an air pocket created under the thermostat after installing a new motor or simply changing your coolant. This air pocket causes excessive heat build up in the engine until the air in the pocket is heated sufficiently to open the thermostat. This added heat is undesirable for any engine, but can be especially true for engines fitted with numerous aluminum components.
The second problem is thermal shock that may occur at the radiator when hot coolant is released by the thermostat when the ambient temperature is near 32 degrees F. Duane Davis, Owner of PRC, observed cracks developing in radiator cores in the area of the inlet in a few rare instances. He noted that this only occurred with customers located in Northern part of the United States and in Canada and only when the owner drove his car in frigid temperatures.
The solution to these problems is incredibly simple. Drill a 3/16" hole in the circular flange of the thermostat. See Photos #1 and #2. The hole allows air to escape from the block which solves the first problem. It also allows a small amount of warming coolant to flow into the radiator at start up to avoid thermal shock and cracks in the radiator.
There are no negative side effects of drilling the 3/16 diameter hole in the thermostat and is recommended for all applications.
Dick Zakrzewski - Streetrod Stuff
Duane Davis - PRC