Hot Rods FlatHead 6 running temperature

I tried searching this up but couldn't find anything. Ive got a 52 Plymouth Cranbrook with a flathead 6. I was just curious what the running temp should be. After about 15 minutes mine gets to about 160 then while driving it goes between 180 and 200 is this normal..Any input would be great. Thanks

 

That's pretty normal. You'd like it to stay at 160, wouldn't you? Well, that requires making sure everything in the cooling system is in tip top shape. Things such as the water jackets in the block and head being clean, the water distribution tube in the block being intact and clean, the radiator being clean inside and out, the pump and fan working right, thermostat working right, the engine being tuned up and running just right, etc.

When it gets to 220, start worrying, when it gets over 230, shut it off and let it cool down.

 

Thanks for the insight. I was thinking anything over 200 is worrisome that's why I needed some help just to be sure.

 

What Jim says is correct. I differ just a little. ASSUMING everything is clean, 180 is ok/better if it is getting there because of a 180 thermostat. I think that if it is going to 200 and does not have a 200 thermostat, it is not all clean. So check that thermostat. Let us know.

Ben

 

I was under the impression from my reading (always dangerous) that the 160° thermostats were a legacy of the days before "permanent" glycol coolants, they used alcohol in those days and higher running temps would tend to boil off the freeze protection.

Engine wear and sludge or contaminates are accelerated with running "too cold" (whatever that is). There does seem to be a belief in general that engines should run as cool as possible, and that isn't really the case. If the cooling system is in good shape the engine should operate somewhere around 200° at times with no problem, I'd think.

 

I thought I heard an engine runs the most efficient around 190-200. My 32 with a full hood, 300 hp sbc with a 180 thermostat and walkers biggest radiator will run 195 to 200 during the summer. I drove it Saturday when it was 45 degrees outside and it ran about 180.
I guess I'm good with the temp around 190/200 because I know it doesn't get any warmer than that. It must be the sweet spot.

 

Yeah, if you want the engine to last a long long time, 190-200 degrees would be good. But old flatheads seem to have other problems when they run that hot, so getting it down to 160-180 is a reasonable thing to do. Modern gas tends to boil away at lower temperatures than it used to, so keeping the engine a bit cooler seems to help driveability.

Every car is different...do what works for the car you have. If it's happy at 200, great. If it tends to vapor lock or have other issues, do what you can to fix the cooling system, so you can run the engine at a lower temperature.

 

Also , how accurate is the older gauge?

 

Flatheads need an asterisk * seems like.

 

Check the opening in the thermostat. It may not be large enough for it to cool at the rated temp. Get one with a larger opening. You can bore holes in the one you have until the desired temp is reached. Have done that before. Hope this helps. L Hud

 

Jim mentioned the distribution tube right off, I would suspect that is starting to rot, but as others stated check the stat, clean the cooling system and check temp with a heat gun or another gauge, I've had those tubes rotted out and removing the thermostat would keep them cool but the back of the block doesn't cool correctly when you do that.