...I agree whole heartedly with the Knowledge offered by the Bosswrench!!
It does Not matter what the Temp Rating is on any Thermostat...as the Engine will Stabilize to the Cooling capacity of the Radiator with the Total of Fans, And Speed of the Vehicle...air flow.
However, the question was brought up as to 'Operating the 351 Cleveland with NO Thermostat in Place'.
Here is what I learned from trying this.
"Yes! The 'Actual' Temperature of THE COOLANT, does run cooler! Because the Coolant runs through the Engine Block and Heads 'So Fast' that 'It' is Not given Enough TIME to ABSORB the HEAT from the METAL!! So the Coolant Shows Cool on the Gauge, While the Block/Heads, and Especially the Oil, are 'Burning-Up'! Yes, the Heater and Defroster is Not Heated and does Not function.
Useing a Lazer Pointed Thermometer, pointed at the Heads/Block, while running with NO Thermostat will prove this as Fact! Coolant Not in contact with the Heated Surfaces, for a Long-Enough Period of Time, in Order to Absorb and Carry Away HEAT, Efficiently. Coolant Gauge Shows it's Cool....The Engine is 'Burning-Up'.
Bottom Line: Never Take out the Thermostat, It Must 'Cycle' as 'Needed', In concert with the Radiator. When Racing, run the 195F! "The Hotter (Controlled), Engine Produces More Horsepower and Torque". The Stat will Open Later, giving the Coolant More time to Absorb Heat...the Engine will Run Cooler as the Temp gauge will Prove With a Higher Temp Reading, of Coolant Sent to the Radiator! Makes Sense? Yes! Cruizing on the Street...run the 180F!
Opposing Views Welcome!
I was Traveling Cross-Country with that '67 Mustang and 390 FE....I was running with the Heater going FULL BLAST, to keep the Engine Stabilized, just below Boiling Over. I stopped in the middle of the Trip, let Her Cool-Down and Removed the Thermostat, Back on the Highway, It Got Worse, Not Better. It Boiled-Over! A little Farther down the road, after cooling, I Reinstalled the Thermostat. Back again to HOT, But Stabilized. I was Cruising for Hours at 100 MPH I-70 Kansas, Eastbound back to Ft. Riley. In the Dead of Summer 1972. The Little Heater Core with the Fan Running at Full Blast, made the Difference. Coolant was 'Straight Water'. Yes!! My Feet were being Cooked and in My Face Like a Blast Furnace, But We Made It! I Loved That Fastback!
...Why Drive so Fast?? I had One Day to Report for Duty. I had a Lover up in Chi Town, later to become My Wife...I drove there First, I think I Stayed for 4 Hours, then Down to Kansas!
...As I mentioned in the Past, After the Engine Rebuild, Break-In and Oil Change...The Return Trip I took from Oakland to Chicago in 22 Hours Flat, Actual Drive Time!! Left Oakland at 1:00PM and rolled into the 'Boulevard of Lights' into Chicago at 1:00PM (by My Watch, Still On Pacific Time)...in the Dark of the previous evening, I had to pull off the Highway and Take a 2 Hour Nap.
That's 2,200+ Miles in 22 Hours On Interstate I-80 Eastbound Averages to 100 MPH...so for every Minute I was stopped Taking On Fuel and Checking the Oil (and Restroom, and drink), I had to 'Make-Up' the Time by Running At 130-140 MPH, when It was Possible! Believe it or Don't! No Brag, Just Fact.
I Challenged Myself to do it. At 1:00-2:00 in The Morning, In 1972, other traffic was near Non-Existent! Imagine Continually 'Cutting' All Apexes, Shoulder to Shoulder, Clear-Over 2-3 Lanes, for Miles. Yes! There were 'Highway Patrols'...There were Also...Doughnut/Coffee Shops!! Those were the Greatest of All Days Behind the Wheel. MJ