Inside thermostat housing dimension?

[hogasm]

I am going to install a coolant return setup. coolant exits the rear of the heads and needs to be dumped below the thermostat. Instead of tapping the housing I am going to make a spacer between the upper and lower housing, and tap it for fittings.
I am going to be lazy here.....
I need to know the inside dimension of the lower thermostat housing

[Arctic Fox]

You do not want to raise the thermostat in the housing or the water will circulate through the block correctly.
If you look at the thermostat you will see a fixed round disk on the bottom of it, this must be seated all the way into the housing in order to block off the hole in the bottom of the housing.
Don't ask me why it was designed this way

[hogasm]

Originally Posted by Arctic Fox

You do not want to raise the thermostat in the housing or the water will circulate through the block correctly.
If you look at the thermostat you will see a fixed round disk on the bottom of it, this must be seated all the way into the housing in order to block off the hole in the bottom of the housing.
Don't ask me why it was designed this way

That is correct. The t-stat fits into a grove in the upper housing.

What I want to do is raise that whole 3c3z-8575-aa t-stat housing and oring from the lower housing.

sorry if my upper/lower wordage is incorrect

[Arctic Fox]

Originally Posted by hogasm

That is correct. The t-stat fits into a grove in the upper housing.

What I want to do is raise that whole 3c3z-8575-aa t-stat housing and oring from the lower housing.

sorry if my upper/lower wordage is incorrect

No... What I'm saying is the bottom of the thermostat has a round disk that has to block a hole in the bottom of the front cover where the stat fits into.
This lower disk is not the part that opens, the upper disk is the part that moves to open and let water through.
The lower disk has to be positioned at the correct depth, if you add a spacer under the stat and raise it up the pump will just circulate water through the radiator but not into the engine block.
Look at the photo (courtesy of BPD).

[sinner6.0L]

you're going to run into the bottom of the cold side cac tube. the stock rad hose just barely clears it