---------- Date: Sat, 6 Feb 2010 12:30:06 -0800 From: tom jennings <tomj@xxxxxxx> On the 195.6 OHV head, the thermostat is in a cast housing waaay up in front of the cylinders. It's clear in the photo below, the little 'pod' that the thermostat lives in. It's a design mistake for sure. http://wps.com/AMC/1963-Rambler-American/Nash-195.6OHV-engine/small/cleanheads2.JPG The water pump wants to suck water from the bottom of the radiator, push it up the block, and into the head; the head is filled with many passageways around all the combustion chambers and exits out the thermostat, into the top of the radiator. If the thermo is closed, water doesn't flow to the radiator, and the cylinder head heats up fast(er). The cylinder head is long and thin. Remember, no water is flowing to the thermostat, so the water there remains cold until it gets how by conduction! You can verify this youself. Engine cold, start and idle. Put your hand on the head (distributor side, or the intake trough cover). YOu can feel it get warm. At some point it's too hot to touch. Feel the bottom of the thermostat pod... COLD! At some point, the head water is HOT HOT, and the thermostat is... slightly warmer... it eventually opens and water flows and it temperature-regulates. ONCE ITS OPEN it works right, because head water becomes thermostat water. Drilling a tiny hole in the thermostat is common, it lets air bleed up to the radiator tank. A "big" hole (1/4"?) will let a decent amount of water flow. I intend to have that water flow past the actuator button on the bottom of the thermostat. Therefore, as the head warms up, head water will flow over the thermostat, "telling" the thermostat how hot the head is. Water circulating will mean like Mark says, even temperature distribution. The downside is it will take longer to warm up and if the hole is too large, the head could run below rated thermostat temperature. But it's just a thermostat, easy to experiment with. -- Frank SwygertPublisher, "American Motors Cars" Magazine (AMC)
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