CARBURETORS : MARVEL
Fig. 3. Warm up or "heat on" position of heat control
lever (J) on instrument board.
Note that (J) is at No. 1, or "heat on" position, and
cam (C) is in such a position that the valve (A) in the main exhaust
pipe is closed; thus the hot exhaust gases from exhaust manifold
enter at (N), pass through the walls or jacket of riser, through
valve (B) i n outlet of riser body which is wide open, then through
outlet tube (M), and out through the lower part of damper body
(L), which is connected to the exhaust pipe which leads to the
muffler.
The point to observe here is that the entire passage of exhaust
gases from the engine is directed by valve (A) through the path
as mentioned above.
As throttle is opened, valve (A) re-mains closed up to approximately
40 miles per hour, then opens wide with wide-open position of throttle.
Fig. 4. Normal driving position. Heat control lever (J) on instrument
board is shown in the center of slot at "medium" or normal
driving position, allowing sufficient flow of heat for normal driving
and moderate weather conditions.
Cam (C) (due to the position of J) is now in such a position that
valve (A) is nearly closed at closed throttle position, but opening
quickly as throttle is opened. Valve (B) is partly closed, restricting
the flow of hot gases through the riser jacket.
This setting of control lever (J) may be used when engine is thoroughly
warmed up, and lower position should not be used except in extremely
hot weather.
Fig. 5. Heat off position. Heat control (J) on instrument board
is shown at the bottom of slot, or "heat off" position,
shutting off the heat flow entirely.
Cam (C) (clue to position of J) is now in such a position that
valve (A) is half open and valy `(B) fully closed. In this setting
no exhaust gases pass through riser jackets.
As throttle is opened, valve (A) will also open to wide open. The
point to observe here is that the entire passage of exhaust gases
from engine now passes. from exhaust manifold (which is connected
to top part of L), through valve (A,, to exhaust pipe, to muffler,
and does not pass through jacket of riser.
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