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Old 03-01-2012, 01:24 PM
BogiesAnnex1 BogiesAnnex1 is offline
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Originally Posted by Infinite Monkeys
I have a transplanted, 1993 Chevy 5.7L TBI motor from a Buick Roadmaster. I can't figure out where one of the heater hose port is. I can see one near the TB unit on the passenger side, on the intake manifold, but don't know where the other might be. Any help would be greatly appreciated.
These ports move around on different installations, basically there is only 2 things going on:

1) a hose picks up pump pressurized coolant ahead of the thermostat which obstructs the return of coolant to the radiator when closed. Usually this is either from the rear of the intake manifold on the passenger (right) side. It can also be from the coolant return ports at the front of the intake manifold before the thermostat.

2) a hose returns coolant to the intake side of the pump (low pressure side). This depending on model and year can be a fitting on the pump, or a return to the suction side tank of the radiator, or a tee fitting in the suction hose feeding the pump from the radiator.

The whole point is to provide a coolant bypass when the thermostat is closed to prevent hot-spot boiling usually around the exhaust seats and spark plugs when there is not yet general circulation; to prevent pump cavitation that would occur with a stall condition when there is no circulation from the radiator; and lastly to provide early cabin heat. AC installations usually include a 3 way valve that shuts off circulation through the heater core when the AC is on but provides a route so the normal bypass circulation occurs. The SBC also includes a bypass drilling on the right side from the head into the block and into the pump suction side, this is to balance right to left side flow as the pump favors flowing to the right side of the block a little bit. It is not intended to function as a closed thermostat bypass being too small for that.

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