Here's a section view from the shop manual:

http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0604.htm

With the flapper completly removed exhaust can go up into the heat box unrestricted. IMO a properly functioning setup is worth obtaining for the cold start driveability it provides.






1952 1300 Canadian 1/2 ton restomod
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