Originally Posted by RWENUTS
The newer vortec motors donít have the bypass in the block connected to a hole in the head. They use the bypass from the intake back to the water pump.
The water pumps are centrifugal type. The fluid is pulled into the vanes at the outside edge and discharge in the centre of the impeller.
The return line from the heater core sometimes goes to the rad instead.
Do these style pumps have the same exterior appearance? Asking due to I had an overcooling issue with a high mileage 4.3 that created a no cab heat condition in the winter. Restricting the coolant return from the heater core resolved the issue 'somewhat'. This motor was a 300K+ unit that was definitely not on the original or OEM waterpump. It looked the same as any SBC pump.