Re: [AMC-list] AND ANOTHER THING 195.6

[tom jennings <tomj@xxxxxxx>]

On Sat, Feb 6, 2010 at 06:25, Bruce Griffis <bruce.griffis@xxxxxxxxx> wrote:

> I was wondering about the drilling the thermostat thing. If the t-stat
> button causes it to open to let coolant circulate, isn't drilling a
> hole in it kind of like leaving it always open? Or is the hole small
> enough so that there is only a small amount always circulating, then
> when it opens it gets enough flow to keep it cool?
>

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.
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