But let me ask you this. By this rationale, wouldn't then the engine reach operating temp much quicker with the heater hoses disconnected than when they are connected, given the extra distance the coolant has to travel? I am now wondering why some folks disconnect their heater hoses.The coolant return is often called a ‘water neck’ in catalogs. The thermostat brings the engine up to operating temperature sooner than if not present. This controls the operating mechanical clearances which are not the same cold static clearances you measured when putting it together at room temperature. Getting the engine up to temp evens out the cylinder to cylinder power because the front pair run cooler than the middle and certainly the rear cylinders. The bypass is used for several purposes but reducing the chill on the front cylinders is a big part of its function while the thermostat maintains the average coolant temp.
The hottest parts of an SBC is the center adjacent exhaust valve seats. GM normally takes he’d coolant off the drivers side head between cylinders 1 and 3 as this is just a bit off the hottest spot in the engine and the first to see trouble if it’s brewing. This is the hottest spot not only because of the adjacent exhaust seats being near by but also with a clockwise turning coolant pump it’s output slightly favors the passenger side, an out come of the direction of pump rotation. There is an internal bypass on the passenger side used to balance the flow slightly, it was eliminated on the counterclockwise rotation serpentine belt drives starting on the 96 Vortec.