Looking for a reason why the PO split the heater line coming from the top of the block next to the carb so that it is also pulling coolant from the clean out spot on the lower part of the engine. You can see the y fitting behind the clear hose on the pic. I will pull inside in a bit and get better shot. Most or all f motors i have seen have the line coming out of the head going into the heater. This truck is pulling fluid from the head and the rear bottom of the block. ( i assume pulling as my thought was that coolant flows from here to the heater.