Here are a couple of pictures Mattelderca.

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1964 Dart GT

With having a 6 blade fan and a shroud on the car it may just be pulling too much air through the radiator. I would swap on a 4 blade fan and see if it helps. Most of our early A bodys had the 4 blade fan and no shroud either.

Rick

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

If the thermostat is properly closed, very little cold water from the rad can circulate back to the engine. Water can't come out of the bottom if none is going into the top.

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1965 Plymouth Barracuda,
225 engine, Quadrajet, HEI, Dutra Duals, 904 Torqueflite, 2.76:1 axle, Addco front bar
Rods & Relics - Fort Erie, ON / Collector Car Tech

Yep, agreed. I asked about the hoses as I have seen some people return theirs to the rad instead of the pump. That might have accounted for extra flow through the rad. It has to have something to do with the thermostat.

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Mattelderca
78 NYB (gone now), two S series, three old Snow Cruisers and a Doo.

This is what I am thinking now. I don't have a 4 blade fan to try, but I will be on the look out. I have tried too many thermostats with the same results to believe it is the thermostat. The thermostat that I have in the car right now is of unknown temp.(no markings) and was in the car when I bought it. I am starting to think it may be a 160', as it is the only one I have tried that has a slight response in the temp gauge. (Heats up to around 160', then creeps up to about 175'-176'.

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1964 Dart GT

so I still have a concern about it not being the fan... While a smaller fan may help, an electric would be ultimate because it will not be flowing air ever unless its turned on (manually by you, or auto by a temp switch, or when the car is in motion)...

However, after going back through and re-reading, I see you are having this issue irregardless of outside air temps (you mentioned similar results in 30* as well as 70* temps). The symptoms all add up to a thermo that is not closed all the way or a thermo that is not seated properly or in very rare cases installed backwards... Even if it were the fan keeping the radiator too cool it would EVENTUALLY get up to the temp range of the thermostat (unless the thermo isnt being allowed to do its job). Also could be the reason why you are having the same results from 4 different stats, and the original may just not be opening correctly, causing a restriction when it should and thats where the slightly higher temp is coming from when you re-use it... Im really about out of ideas for you, and Im sure someone will still chime in and say Im wrong in one way or another, but obviously something is not normal about your application.

You can also run the heater hoses across the intake manifold intead of the fender, this will isolate more heat to the engine itself and not allow the heater hoses to cool themselves...

Have you ever compared temps without having a thermo in there at all?

oldskoolracer: Installing thermostat backwards will result in quick over heating, and hoses puffed up nice and fat... Don't ask how I know this. Think about it; the coil the reacts to temperature is suspended in air or cool coolant from radiator unable to see the head coolant temperature and blocks flow.

I too agree that there is a problem with thermostat's mounting or fit that is allowing enough coolant to bypass disallowing full warm up.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I find it easier to set the valve lash with less stuff in my way,that's why I ran the hoses there.
I am not installing the thermostats backwards, and they fit perfectly in the groove in the housing, I have run the car without a thermostat, it heats up even slower than with one, but does not exceed 180' ever.
I am waiting on some more thermostat gaskets, as I have trashed the one I had on there. Hopefully I will get to experiment with looping the heater hoses this weekend and see what results in taking the heater core out of the picture.

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1964 Dart GT

I live in -0°F Wisconsin.

So ya say the motor is warming up but the Car's heater isn't and you've exhausted every mechanical option underhood, except electric fans, which would pull like the 6 blade fan. So did you know your blend door is contorlled by a cable which occasionally needs adjustment? Loosen the clamp on the cable shield and close the door fully while the lever is slid to maximum red or hot. If bet real money you suddenly have hot heat. Plus, you could reverse flush the core. The coolant flows from behind the thermostat to the core to the water pump for suction.

6

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Slant six should have stayed in production.

Aluminum Six- This thread has gotten too long.
Problem: Car does not get hot.(Max's out at 176-178 degrees) Heater works, but only blows warm air, because car is not getting hot.
All heater controls function properly, I have switched between (4) different thermostats (2-180,195 & mystery temp.) with no really change.
All hoses get warm, with lower hose being the coolest of the 4.
I blocked the radiator (partially) with cardboard on a cool day here and the temp went up above 180', that is why the 6 blade fan and shroud became suspect. I am not an electic fan fan , so I am going to try a 4 blade fan.(when I find one.)

On a different thought/question. Did A/C cars have a different size waterpump pulley?

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1964 Dart GT

It is very difficult to install the thermostat incorrectly and the hardest part is keeping it seated in the groove until the housing is bolted down. The important thing is to make sure that the pellet is facing inside the cylinder head.

Your photo appears to show the water supply (from the cylinder head nozzle) is connected to the right hand heater core nozzle (looking at the firewall). On my 65 and likely your car too, the inlet is on the left side and the outlet on the right. Connecting it correctly helps air to purge out of the core.

In the winter, you will likely not need a fan at all. IIRC, Sandy in BC drove his 65 Valiant for many years without one year-round. The fan only serves to increase heat transfer through the radiator (mainly at low vehicle speeds). It is ONLY the thermostat that regulates temperature - the fan only affects how fast the radiator can reject heat. Even if you've tried several already, a defective thermostat is the only possible reason for your low operating temperature.

Also, the air coming out of you heater should still feel hot with 176-178° water. If your heater hoses aren't too hot to hold when the engine is at 176°F, you aren't getting enough flow through the heater core.

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1965 Plymouth Barracuda,
225 engine, Quadrajet, HEI, Dutra Duals, 904 Torqueflite, 2.76:1 axle, Addco front bar
Rods & Relics - Fort Erie, ON / Collector Car Tech

I wasnt reffering to you putting it in backwards, just throwing an off the wall thought out there of things I have seen or heard of people doing. Also what I mean about it not seating proper is not being sandwiched tight between the head and thermo housing, not something you can see once its together but if that is the strange phenomenon that is happening it would act as a thermostat not closing all the way. Again, just another "out-of-the-box" thought since you have already ruled damn near everything else out.

Sorry for lengthening this post, but you may be on to something there with pulley size. In a 1962 down Chevy inline application pre 1954 installations need the shaft hydraulic rammed or cut down an inch to fit, and have to use the pulley they came with (wider belts start with 1950 back so there's a few years window) the point is cavitation. Chevy people swear if you use the old pulley the fan will fly apart because it's almost half the size so spins 2x fast and you will cause cavitation at speed. Never heard of it anywhere else but I do know aftermarket AC used fabricated everything and the whole idea behind slanting the 6 (besides hood clearance) was to move the water pump off the front of the block to the side. To shorten the engine. Lucky for us the market at that time considered V6 to be odd, like the I5 Colorado more recently, or this may have been the nothing special V6 board.

6

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Slant six should have stayed in production.

I wasn't aware that it made a difference. I hooked it back up like it was when I rebuilt the engine. Are there any indicators on the heater core?(for direction of flow? I don't remember seeing any?)

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1964 Dart GT

Check your service manual. You can also figure out the correct orientation by looking at your heater core. The inlet nozzle connects to the lower part of the core and the outlet connects to the upper part.

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1965 Plymouth Barracuda,
225 engine, Quadrajet, HEI, Dutra Duals, 904 Torqueflite, 2.76:1 axle, Addco front bar
Rods & Relics - Fort Erie, ON / Collector Car Tech