That's cool! Sounds like those were good engines. Not a lot of turbos were cooled till later on.
Some of the piston aircraft engine turbos I used to work on had no cooling. Smart owner/pilots would let them idle for 5 or 10 minutes to let the turbo spool down.
If they didn't the turbos would coke up and the waste gates would stick.
If the turbos coked up bad they would get rebuilt.
My old boss found out that the old Mopar Heat Valve Solvent worked well on the waste gates. We would soak them and then hit them with a rivet gun on a piece of wood.
Most of the time that cured them. Those engines were turbo dependent so no turbo, no power.