Stant 13469.
Bottom flange is .672" diameter.
Flange to flange cold is about .837" measuring from the side of the large flange closer to the small flange.
Open is ~ 1.080" flange to flange. Hard to measure. a 195 degree thermostat starts to close fast when pulled from boiling water.

 

I see that you measured yours with a set of calipers, as did I. Flange to flange should really be done with a depth gauge. I'm sure that you, like myself, were kind of eyeballing that measurement.

 

I started getting depressed after this next set of measurements.
1st picture; I used a telescope gage to establish the diameter of the water pump bypass port. 2nd picture the size of the bypass diameter is 0.7674”. 3rd picture; depth of thermostat recess to top of block .0753”. 4th picture; depth of land to top of block 1.122”.
Depth from a thermostat’s large flange to small flange to seal off bypass: 1.122”-.0753”=1.0467”, this will work compared to the thermostat dimensions stated. However the bypass hole is more than .100” larger than the thermostats small flange. Without a balanced thermostat skirt shutting the bypass hole off, the bypass is only restricted. It would be good if someone could make the same measurements for conformation purposes. I am sure of my measurements, however i am not sure of the origin of the engine.

 

I would say that with all dimensions stated of thermostat and block, that the RT and Stant will work as designed. Hot parts that are mass produced and cheap to manufacture will not be high tolerance.

Given the port dia. and t-stat cap, a "restrictor" is as-intended.


Great news if you ask me!!

 

I actually tried to build up the flange that closes off the recirculation hole with solder to get closer tolerances. Almost had it when I passed the torch flame across the spring consequently taking temper from a coil. AAaargh! Said to myself, to heck with it, and bought a new thermostat and installed it as delivered.

My whole thermostat adventure started when I tore down my engine and found, among other things, a standard Windsor unit under my radiator hose connection. Went to the auto parts store and they tried to sell me the same thing. I said no way, so they showed me the computer screen. My response was that I didn't care what their computer said, it wasn't right.

Garbage in, garbage out.

 

When you measure things of this nature down to fractions of thousandths, I think you are just showing off.

Nice "tools" BTW.

 

I don't mean to show-off. I just have 35 years in tool and die, its just habit.
I just take my wife with me to places when I want to show off. That's what I tell her anyway!

 

I saw this, however I don't recommend it.
If I was to ever restrict or close off the bypass port, I would add a inline thermostat bypass which would the go back to the pump. But I have no plans like that.
SOURCE: Water Restrictor Plate - 351C - New ~ 1970 - 1973 Mercury Cougar / 1970 - 1973 Ford Mustang (53234) at West Coast Classic Cougar :: Specializing in 1967, 1968, 1969, 1970, 1971, 1972, and 1973 Mercury Cougar Parts
New water restrictor plate for the Mercury or Ford equipped with the 351 Cleveland engine. It has been an accepted fact for decades now that the 351C bypass system was not the greatest idea Ford ever came up with. The unique 351C thermostat "hat" never seals well, causing a certain portion of coolant to just circulate through the block and never make it to the radiator. Years ago, Pantera enthusiasts (all Panteras had cooling issues from the factory BTW) found that if they soldiered a penny into the hole in their restriction plate and used a standard small block Ford thermostat, their cooling issues all but disappeared. That trick worked fine until Ford discontinued the brass restrictor plate. This aluminum unit is designed to replace the brass plate and be installed as-is. This unit must be used in conjunction with a standard thermostat , you cannot use the 351C unique thermostat with this block off plate. The tiny hole in the center is for air bleed only. Want to find out how to use a penny instead of spending $21.85? Click hear to learn more!

On a record hot day in Evansville, In at 108 degrees the car was driven a while. She never went over 200. Im so happy with this upgrade, get the WCCC part and a 160 thermostat and your problems are cured!

Replaces Ford Part number D0AZ-8K517-A.