So, I installed a cutoff valve on the top hose running between the heater core and the thermostat housing. When it is open, my temperature gauge indicates that the temp rises as the engine warms up, and stops at 180° when the thermostat opens. When the valve is closed, the temp rises to a bit over 200° before the thermostat opens, and the gauge quickly drops down to 180°. So my question is, would moving the valve to cutoff the hose between the core and the water pump be any different? Also, to anyone who has installed a cutoff, do you notice this same thing and is it something you just live with during the summer when the valve is closed? My truck is a '51 3600, and my particular heater will not allow a Ranko valve.
