[AMC-list] quiet in here, 195.6 ohv cooling system

[tom jennings <tomj@xxxxxxx>]

Everyone must be out driving.

I have been insanely busy, got a new (part time) teaching job for the fall
(contract signed), a huge art construction job (contract NOT signed) and a
small art construction job late fall. Looks like I'll actually get paid,
wow, I know money's tight everywhere (except for the (trans)national
corporate thieves but they probably don't drive AMCs).

I've been simply driving my American with the stock pump and no oil
filtration. It runs great, but still haven't got the idle right, not sure
it's carb (bad timing scatter too) but too busy to do anything about it.
It's very stable and non-harmful.

I now have all the parts to do the full-filtration right, and the 'funny'
part is, it's unbelievably easier than anything I started with. A new cover,
a blockoff plate/gasket, two hoses, filter bracket, filter, done. It'll be
full-flow again before I drive to work on Tuesday. (I'll probably do the oil
change a bit early since I ran it unfiltered for 500 miles or so, and I'll
switch to Mobil 1 15w50.)


Got a decent test in of the cooling system. Here's another weak design point
of this engine (or operator error).

My new teaching gig takes me to Valencia CA once a week, so I climb the
first serious grade on I5 North, what 6%? pretty steep for a freeway, 5
miles of it or so. The water jacket between cyls 2 and 3, normally same as
coolant outlet, 185 - 190, got up to 210, 215 degrees F peak. That's in 3rd,
carb secondary opening, 8InHg, no OD, 45 mph, 2200rpm. Ambient was 90 plus
and humid. Totally fine.

But on the trip to the AMCRC event weeks ago I took the same route, ambient
was lower, but I did the whole climb up and over the summit, THAT was work
for this car. On that trip I ended up in second gear, 2500 rpm (it gets
steeper!), cyls 2-3 got up to 230 degrees, coolant was "hot normal" (factory
gauge only on the thermostat neck). I couldn't recall what the boiling point
of 50/50 antifreeze was so I pulled over to let it drop, which it did, just
fine. There were no side effects, no boilover, no bad noises, car ran great,
factory temp gauge showed 2/3rds to the top, etc. If it wasn't for my head
temp probes the situation would be completely normal.

This engine's cooling system is mechanically impeccable: boiled out block
with 4000 miles on it, new radiator, new hoses, new water pump, new 180
degree thermostat, my to-me-proven head cooling hack, TWO high volume
electric pusher fans with good sealing. Radiator fins all open. 13lb cap.
50/50 coolant (new).

But 50/50 boils at 223F, so it most definitely has localized steam pockets
or at least steam bubbles on the inner surface of the head water jacket.
This has got to add stress to the head casting. Yet ANOTHER small but
significant source of trouble in an already troubled head design. If you
look at the sliced up head you can see that that area between I and E valves
in each cylinder is all sharp edges and the skinniest, uselessest water
space around the exhaust valve. Uneven cooling!

I have no idea what the inner guts of a 232 head, say, would be under these
conditions. I'm fairly confident of my probe placement, as it usually runs
within a few degrees of the coolant outlet temperature (though I have only
the dash gauge in the car at the thermostat, I have a hand-held IR probe
I've checked with multiple times).


Or maybe it's operator error: maybe it's just unreasonable to drive an
antique car engine on a modern freeway at these extremes? We know this ain't
no 232-->4.0, which excels under all this, and you can't really blame Nash's
1930's design for not anticipating 2010 traffic needs.

So here are the things that to me have added up to  problems with the 195.6
OHV head (headgasket leaks, cracks, etc):

* No head water circulation during initial warm up! (MAJOR design flaw)
* Poor headbolt pattern and sealing surface widths (design flaw)
* Poor head and deck flatness at rebuild time (cheapskate "old car"
syndrome)
* Poor water circulation/flow within the head (design flaw)

The thermal stress cycles back out the headbolts, dropping sealing torque,
coolant loss ends up with overheating which increases thermal effects in a
positive-feedback manner. Not. Good.

Luckily those are all easily fixed, though the ARP stud set cost $150, it's
just I've never heard of anyone bothering spend any time on this motor
besides me, Frank, and now Dave. Surely some Nash club person knows as much
or more. I guess I should go seek them out.
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