Grumman S2F/WF/TF Engine Nacelle Detail

Every once in a while someone asks a simple question about an airplane I happen to know quite a lot about and I don't know the answer. In this case, it was the engine exhaust system on the Grumman S2F/WF/TF (S-2/E-1/C-1). The upper exhausts are obvious (this is a picture of an early S2F-1):

The question basically was, did the exhaust gas from all of the cylinders come out here or were there other exhaust stacks on the nacelle. You'd think the answer would have been included in the S2F monograph that I wrote with Bob Kowalski (see http://tommythomason.com/books/grumman-s2f/). It wasn't.

It turns out that in addition to the two troughs on the top of the nacelle there was a third, virtually identical one located on the bottom of the nacelle:

It ended at the forward edge of the oil cooler door. Note the convex stiffener running longitudinally down the center of the trough. The oil cooler door is open in the following picture:

My guess is that there were also two pipes located here that were the exhaust system for the lower four cylinders of the Wright engine.

This is an illustration of some of the engine nacelle panels:

Item 11 is the panel that includes the lower trough. Item 10 is the oil cooler exit and door. Item 4 is one of the two upper troughs (5 is an insulation blanket).

Interestingly, this trough is represented on the ancient Hasegawa 1/72nd S2F kit, another example of its high level of accuracy particularly compared to the much newer 1/48th kit from a different manufacturer...