Was the pilot Polish ?. Rex Nawalaniec ?
From memory that’s the transmission oil cooler on top of the engine mount with the duct attached to the exhaust pipe. They tried to draw fresh air through the cooler augmented by the fast moved exhaust gases in lieu of ram air.
Because of the extra power of the Allison, the limiting factor was the torque the transmission could absorb, hence the overheating.
No power controls, hence the cyclic shake. Keeping the head and blades in dynamic track and balance was an art. Made easier when the Chadwick Helmuth gear came along.
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