Exhaust Spring-actuated valve thingy

[mikeiidc@domain.elided]

Dennis Millward and I were playing around with my '70 or '71 800 today,
and I was changing out the exhaust donut, as there was apparently a
terrible leak coming from it (passenger side).  In taking it apart, I
found that there was a spring mounted cylinder running through the
adjoining piece between the exhaust pipe itself and the exhaust
manifold.  It had a round spring on the outside, then a cylinder that
ran straight through this piece, and was anchored to the other side.  It
was basically like an axle, and we thought it may have housed some kind
of valve originally.  It also reminded me of the interior of the
automatic choke on my '68 Travelall, because of the spring, but the it
wouldn't have needed the "axle" to go straight through the exhaust, it
seems.  Anyway, anyone know what this is?  Isat the thing someplace and
can't rememebr where right now, so I am describing it from memory.  It
had a small piece attached to the outside that moved around when the
spring heated/cooled as well, but I saw no place for anything to attach
to it.  Was this a piece that had a rod going up to the carb as a choke
release when the engine was warm?  It was only on the passneger's side
(same side that the auto choke would mount on if my carb had one!), and
we checked my '73 Scout II, my '68 T'all, my '74 Wagonmaster, and
Dennis's '63 3/4 ton PU,and none of the others had it.  Any
ideas/knowledge of this part out there?

Thanks!

Michael