Timing is what made the big difference for me. My timing was way off and it made me overheat no matter what kind of driving in about 20 minutes.
Im usually fine now, but on a hot day and/or if I get stuck in traffic especially on the highway where the car was just prior running hard down that road she'll rise up into the 200-212 range of temperature. But then if I get moving again and drive the engine easy she'll slowly cool down back to 190-180.

I've kinda got into the habit of treating my Ford like a motor cycle with an air cooled engine, realizing I gotta keep moving to stay cool. So since I'm familiar with the city Im in I'll avoid routes with traffic and lots of lights.

Well like many things automotive there is usually plenty of misinformation out there by some with how things actually work. Y Blocks aren't especially known for overheating issues compared with some engine platforms, seems to me.

But generally when there is a true overheating issue, a lower temperature thermostat isn't really much benefit, and poses other problems as you point out. They do tend to slow the engine warmup, and maybe delay the onset of boilover. Thermostat maintains the floor on engine temperature, not the high side - I see this fact overlooked or misunderstood a lot.

Really clean internal coolant passages, and a "rodded out" radiator with same seems to be key to any cooling system. Sediment and scale buildup on older engines cause trouble no matter what.

I listed above how i fixed what i felt was too much temp earlier. I run a 160 thermo and since have learned 170 was standard and NAPA sells them. Look up under Mopar vehicles I will make that change when I get a chance.. By the mid 1960's manufacturers raised their temps in cars; a 1965 GM car i had used a 195 thermo which I left in until I added an AC unit then moved to a 180 and everything was good. 
If you have a recovery unit on you car watch it. If not and you run 1/2"to 3/4" low in the tank as when the car was new and your not loosing coolant I wouldn't worry about it. If it does, do the smaller pulley and get peace of mind when in hot weather with in town driving.
Fuel mileage is better when hotter along with burning off condensation or new cars wouldn't be that way. Good Luck

56 Vic, B'Ville 200 MPH Club Member, So Cal.

What is the "sweet spot" temperature for Y blocks? I've noticed the tendency in general for a lot of vintage car enthusiasts is to run 160° F thermostats. Let's leave Flatheads, tuning for maximum horsepower and icing down intake manifolds kind of stuff out of it. What operating temperature are we looking at as optimum? What did the engineers shoot for?

When I read the Operator's Manual, it states that the 160° thermostats are for use when using alcohol-based or methanol antifreeze, and "185-195 degree thermostats provide better fuel economy"; the '64 Shop Manual goes on to list in the specifications that for "all engines" that thermostat opens from 185° to 192° and fully open at 210° to 212°, so it seems to me a 195° F is right in there with the design spec, but this choice will never come up in the aftermarket catalogs or cross reference as a suitable choice.

Some will even suggest in a general way that the 195° F thermostats are a smog era emissions creation. This doesn't seem to be the case.

An early spring roadtrip I took last year left me a believer in the 195°, using a 180° F thermostat, a strong bitter cold wind left the heater unable to cope even on full blast. Normally the heater will run you out. I think a lot of people might have swapped between a "winter" and "summer" thermostat, but I'd like to run a 195° year round, even in summer. Any insight into this, the conventional wisdom versus the black & white in the manuals?

OP: one thing to check is the distributor advance, make sure the distributor advance plate isn't sticking, centrifugal mechanism moving smoothly throughout RPM range, and the vacuum advance is working as advertised. Retarded ignition timing will run very hot and is sometimes overlooked.

For 13 years I struggled with our ’56 Thunderbird overheating, particularly at low engine speeds.  Then four years ago, I reached my boiling point and engaged a project to identify and resolve the issue.  ASU Now recently did a story on the project that you can see at: https://asunow.asu.edu/20180403-solutions-making-thunderbirds-cool or you can see the details on our website:
https://pti-az.com/
 
Casting Flash
 
Cooling Research Detail

http://forums.y-blocksforever.com/Topic135031.aspx

I followed Greenbirds advice 6 yrs ago with a smaller pully. Bought mine for a 60's Mustang along with a spacer kit from Summit. I also added a plug to the bypass hose and drilled a 1/8" hole in it. With these two changes I was able to use a 4 blade fan to keep the noise down. I believe a 180 thermostat should be your max and remember your radiator is not the only item in your system that sees the pressure. I use a #7 pound cap. Good luck.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

At 1000 miles Id say it should be settled in...but? . As others have said check with a good gauge and infrared . Thermostat would be best at 180, but Im sure what you have is fine.



"Came too close to dying to stop living now!"

If You measure your Diameter You should be able to find One on Ebay. Many of the Ford V-8 Pulleys can Interchange. Just check the Height from inside the Pulley to the end of the "Snout" sitting on a flat Surface. If You know what Diameter Yours is someone on the Site may have a smaller One. 7" seems to be a popular stock Diameter. Try and find One 6 1/2 or 6 3/8. Put an ad on the Classifieds Section..

  

All great ideas everyone. I will check with my infrared tester and consider a smaller pulley.

Anyone know of what pulley and where to get it on line?

My 55 TBird ran hot idling in traffic.  I replaced the stock radiator with a three row Champion aluminum radiator.  I also removed the stock fan and installed an electric fan in it's place.   The whole package cost me less than $350.   Now I don't have to hear the old "wind mill" fan and my car runs 170 degrees in hot Florida weather.  Best upgrade I ever did.