It's supposed to swing in on the bottom and out on the top. It's purpose is to reduce draft over the fire and is adjusted using a draft meter. If you don't have a meter, have it checked out by a pro. Don't adjust it yourself.

Thanks Baymee (again). My friend's works that way but mine was apparently installed upside down or backwards? It swings out on the bottom and closes shut tight once the flow gets going. When I posted a few months ago about how a delayed ignition would cause a burst of smoke out the damper that's when it would swing out at the bottom. Once the fire started it would close shut tight via suction. Should it be open (tilted inward) during suction? that's how my friend's furnace works. It's not possible for mine to swing inward at the bottom the way it's set up now, it only swings out at the bottom. Hope that makes sense?

You should be able to remove the hex head screws and pull the damper out and re-position it. The pin that the damper pivots on must be horizontal. The weight is a round knob and that should hold the damper closed when there is no draft (not always). When the burner starts, the bottom will swing inward and regulate the draft to a negative .02 over the fire. That's why you need a draft meter.

In your situation, you have the full draft over the fire and depending upon how much draft, you are greatly reducing the efficiency of your fire.

Ugh, we moved into this house 4 years ago and this thing has been in the wrong position all this time. Makes me wonder how the interior of the chimney looks and if this has caused soot build up in there? Once the furnace starts up it doesn't take but a few seconds for the damper to shut tight and cut off that source of air flow up the flu. I'll tinker with it this weekend to see if it can be easily reversed.

You weren't suffering from a lack of combustion air; most likely, you had too much air and lack of heat transfer in the exchanger.

I hear Angelina Jolie's flue damper swings both ways.

WaaLaa !! Well I fixed (reversed) the swing damper and it appears to be working a-ok. I still have a little delayed ignition problem about every 4-5 starts but now when that occurs there is No smoke forced thru the damper opening because it's closed and will only open inwards after the furnace ignites (takes about 5 seconds to open). It also seems that the furnace now runs for a bit shorter duration before cutting off so you were right Baymee (again) about not getting top heating efficiency with the damper swinging out. Next time my furnace guy comes over for the annual tune-up I'll chide him on it, ha. Thanks for the good advice!!!

you're welcome

Hello: I have a semi-related question... found my draft damper wedged nearly shut by the oil technician who just performed the annual tune & vac today. He inserted two sheet metal screws, wedging the damper at opposite ends so that it will not close nor open, leaving a slight opening (the width of the screws). I called the oil company and they explained that I have sufficient draft with the screws holding the damper slightly open, and I should leave them in place. Wanted a 2nd opinion.. my concern is that this may be some gimmick to make the burner use up more oil. Any comments? Thanks !

Get in a different tech. Someone that has SOME idea of
the workings of an oil furnace. That is not right.
F.Y.I. an oil burner will burn no more fuel than the size of the nozzel that is installed. providing it has the proper nozzel to begin with. a draft regulator is
calibrated to the hight of the chimney. I raized the roof
of my garage by 5 feet and had to recalibrate my draft
regulator because it would never close even without the
furnace running. That was after raizing the chimney to the
proper hight.( natural draft ).