[AMC-list] 195.6 ohv heater, valve, and mystery solved

[tom jennings <tomj@xxxxxxx>]

Last night driving home I figured out the source to a Great Mystery in my
American... the symptom that led to figuring it out was, if I pull the
heater valve all the way out (full ON) the car... overheats?!

A few months back I had a radiator top-tank leak; I removed and resoldered
it in place (turns out had a chunk of crud under the neck so it couldn't sit
flat so the thick solder seam eventually cracked and leaked). Easy fix. But
when I re-filled it, cold, idling in my work spot, I felt the head get hot,
but the thermostat wouldn't open, and I got boiling in the head! WTF! Turned
the car off, the guage read HOT, I let it sit, the thermostat eventually
opened, it sucked in a bunch of water and then was OK. Very strange. Did
this two separate times!

I'll spare you the rest of the details -- here's what the root cause was.

** When I flushed and refilled the radiator, I did so with the heater valve
open. Of course. Well... as anyone with this engine knows, the heater water
control valve gets rotten after 40+ years (not even half a century?! must be
a quality problem). Being too cheap to spring for NOS I put in a pipe nipple
and used a nice, modern replacement valve from NAPA. Fits and works great.
The heater core died also, long ago, so I fit a nice Ford Econoline heater
core in. That works great also, took a small mod to the heater box to fit
it.

Well the heater system diverts water from the water pump to the back of the
head -- and with the new valve (bigger bore) and new heater core (likely
higher flow) it can actually bypass enough water to short-circuit the
radiator!

D'OH!

I will consider a restrictor for the heater hose, but for now, simply not
pull the valve out all the way. I might be able to simpyl adjust the wire
pull, but the strokes etc are such that I think that won't work.
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