Home Forums Gear Hunting Trucks and Four-Wheel Drives 1978 F-150 shot box 4x4- New project

have a look at this link, it does a good job of explaining why you need the right stat.

http://www.are.com.au/feat/techt/thermostat.htm

that bipass port I believe runs to your pump & shares an inlet to the pump along with your heater core return hose.

So, unless that bipass port is blocked off by the stat your pump aint gonna pull much at all through your heater core.

The link explains it very well.