Zitat:
The dowel supplied is to block off the water pump bypass which is on all stock water pumps.
This bypass circulates coolant until the tstat opens, so as not to create engine hotspots and pump cavitation. Some people tap this hole in the block and screw in a brass allen socket pipe plug instead of the dowel.

Some aftemarket high performance pumps do not have bypass flow built into them. This is based on the theory that more flow will occur without the bypass for better high performance cooling.

If you use the dowel, then you must drill a few 3/16" holes in the tstat so that there will be a small amount of flow.

These holes serve 2 purposes, 1 for burping the air out while filling the system and 2-for creating necessary flow until the tstat opens. It also can be argued that the tstat will be more responsive at intitial warmup with the holes.

BTW Jims73SF