orchard 22 heat box adjustment?

Hello again,
I was wondering how does one go about adjusting the butterfly valve(or is it a flap?) that is located inside the heat box on an orchard twenty-two? Because it appears to be running VERY HOT, to the point that you could fry an egg on the hood and I am running it minus the hood for now. To me the book appears rather vague on the subject and I would rather do this in an educated manner so as not to further damage my already damaged heat box(has a big crack where the box meets the "ear" on the left side).
P.S. I finally got it back together and running, and driving, and working again (discing a field) 😄 finally! 2-3 yrs. of work is paying off!

thanks,
Orchard22

hello again,
I am still in need of assistance and any and all comments are appreciated!

Hi O22,
here is a scan from the 22 OMI.
Hope this helps.
Cheers,
Eddie B.