If a car is running too cool at highway speeds (160ish) but runs fine in stop and go traffic 180-200. would that be an indication of too cold of thermostat? i think i had put a 180 in the 340, but gonna try putting in a 195....thoughts? (afco alum rad and elect fan)

The thermostat sets the low end of the scale. If you have a 180 degree thermostat in the engine, when the temp drops and nears 180, the stat will start to close. That restricts the flow and lets the temp rise again. The engine should never be able to drop below the thermostat rating if the thermostat is functioning. If your engine really drops to 160, then you most likely have a 160 degree thermostat or the one that's in there isn't closing when it should.

Or your temp gauge is less than truthful.

Kevin

Ya I considered the gauge too, but my heater doesn't put out any heat so I ruled that out.
So, if I install a 195 stat, my elect fan on/off switch choices seem to be 185 or 195.
Wouldnt run this setup cause the fan to run constantly?

That's what I think would happen...don't want that. Maybe I should try another 185 stat first ?

I would, (Keep It Simple Sam). If you are sure the gauge is correct (I dont trust em to be dead on). 160 is too cool & will cause fuel atomization problems. poor mileage/fuel wash. a 190/195 would be even better & reconfigure the fan however which way it needs to be to deal with it

Why not pull the stat and see what it is FIRST instead of assuming what you installed ?

Even at 160° your heater should put out plenty of heat. My Dart has a 160° stat in it and the heater works good. I drove it yesterday and it ran about 170° in 75° or so air temps.

Same here mine runs about the same except in hot weather(90)then about 190-200.If thermostat is your problem put a 160 in there and you don't have to worry about it.

That is one definate advantage to adjustable fan controllers. The OFF temperature must be higher than the thermostat temperature to avoid running the fan onto a radiator that is not flowing coolant.

160 degree water will definitely run a heater. Maybe your heater core is plugged.

I salute you for understanding that 160 is low for a non-race engine.

After you check what you have in there and check where it opens using the hot water/thermometer testing method, put a 180 or 185 thermostat in it and a 195 fan switch.

One of my cars had a problem with the thermostat sticking open. It was replaced by the dealer on a TSB.

R.

looks like the thermostat was at fault, i remember buying a mr.gasket brand stat now, and it even has 180 stamped on it. installed a 195 stat (stant) and it runs much warmer now, but will prob switch it out for a 185 as my fan setup is causing the fan to run constantly at 195. 185 should work with my current fan thermostatic switch.......hopefully?

The Mr Gasket stats earned a reputation for problems... though the one I had for a while was fine. 180 degrees is a standard temp and probably fine for your application. A standard 180 stat from the AP store should do well unless you are running a high volume water pump. With high volume pump a high flow stat is recommended. I am currently running the Milodon high flow 180 stat from Mancini w/o issue.

160 should give you plenty of heat inside car. check temp of supply and return hoses . .