I visited the landing gear at Bear Swamp Hill early Sunday morning but did not stay long because Jessica wasn't feeling well. I did get another photo to compare to the one I took back around 1975 or so.
Yes, your photos show the speed brake.Not sure if this is the same part as above. these pics are from 2020. I recently visited again and could not find them . cant believe someone would take a big part like this
The speed brake is the very back of the engine where the flame comes out. Basically, they open them to slow and close them to make the exhaust hole smaller to get more thrust.
That is interesting. I think the plane was an F-105, wasn't it? Here's a photo of the speed brakes on that plane. I can see how somebody might have the impression that its purpose was to constrict the exhaust. But, as you say, the real purpose is to create drag when it is opened.
https://www.reddit.com/r/aviation/comments/2nrbqs