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post #1 of 30
Thread Starter 
Ok have the older smokey mountain smoker am tired of having to add chip or chunks and don't like the fact they don't burn to ash. So after looking around on here did the mailbox mod but since made a different box all together. Bought an amnps 5x8 and tried it out mainly wanted it for long hot smokes not much into cold smoking yet. Anyhow after having trouble emailed back and forth to todd didn't realize most the mailbox mod smokers were elec. Ended up getting a 12" tube smoker and tried different spots in smoker and either caught fire or smoke was on the lite side. So tried the tube in the box and if I put a computer fan over my vent hole catches fire and no fan little smoke and also think the flame is affecting some of it. Looking for ideas. Might sell the smoker and get the masterbuilt xl.




post #2 of 30

Fordman, evening.....  Hey, try adding a chimney from the "smoke" inlet to just under the lower food rack....   What may be happening.....  smoke enters the Cook Chamber, and recirculates and gets consumed by the flame...  If you redirect the smoke to just under the lower food rack, that problem might be eliminated...   Also, if you have a cast iron fry pan or griddle or trivet, try putting that above the flame for some thermal mass and redistribution of the flame and heat...    While you are at it, you mentioned the chips stay black and don't turn to ash...  add a couple 1/2 - 1" holes near the top of the smoker, on the side wall about 1-2" below the top....  that should help in Cook Chamber air circulation.....



post #3 of 30
Thread Starter 
Well thought about doing a TP over the flame to protect the smoke but I do have a big cast iron pan I could try also. Two guys at my work have the same smoker and the same results with the chips or chunks going black not ash figured if was nature of the propane. I modded my exhaust as well the first pic is the original vent then changed to a 4 in pipe but then thought was to big so went to a 3 inch that is in pic. Have another flange and thought about cutting the straight part off and just making a different stack.

post #4 of 30

Everything looks like it should work well...   I think the flame is consuming all the oxygen..  that's why the black chips...  You are making charcoal.. as far as the lack of smoke.. I'm at a loss...    I hate to say this but maybe it's just the nature of the beast..... 




post #5 of 30
Use the AMNPS and leave the door of the fire box open an inch or two with no fan. I think those two holes are too small and too high. Also the propane flame can burn the smoke so you can't see it but if you can smell it coming out the exhaust then you are still getting flavor from it.
Here is my setup on my GOSM and it works awesome. You can't see it but I have a 3" square hole on one end of the toolbox for intake air.

Post #7 of this thread shows my testing phase and you can see the intake hole. The test worked perfectly so I just duplicated it on the final:
post #6 of 30
Thread Starter 
Also the propane flame can burn the smoke so you can't see it but if you can smell it coming out the exhaust then you are still getting flavor from it.

Yeah but I personally like go see more might have to prop the door open and try that. My thinking on the holes being that high was to create a cross draft over top of it to keep flare up's down.
post #7 of 30
I'm also wondering if that 90 on the exhaust stack is slowing down the airflow.

I also cut a 2" square hole in the top of mine along with the factory damper and I get great draft through it.
post #8 of 30
Thread Starter 
You have a lower damper all I had is the exhaust one
post #9 of 30
Mine isn't the Big Block so it doesn't have any lower intake vents, just the hole around the burner in the bottom, and now the hole I cut for the external firebox. I have the factory exhaust vent with damper and then the hole I cut in the top.
I really think the reason you are having a problem with the AMNPS is airflow, the AMNPS needs a lot of air. The tube will burn with a lot less air, that is why they have been working inside propane smokers with no mods where the AMNPS won't.
post #10 of 30
Thread Starter 
Do you get smoke escaping out the extra hole at the top instead of the exhaust vent? Any pics of your extra hole
post #11 of 30

Ok have the older smokey mountain smoker am tired of having to add chip or chunks and don't like the fact they don't burn to ash


In my opinion you DON'T want the wood to turn to ash


If you get this


...you are getting flavor from the wood.





  • A piece with some life left in it.



  • Smoking fine, I remove the chunks after they turn black and there is no more smell then I  add fresh chunks.
  • If I let it go past this point, it smokes excessively right before turning to ash, I do not prefer this end smoke.





Charcoal is then recycled for other things.

post #12 of 30
Thread Starter 
No matter how long I let it go never turn to ash same goes for the other two people that have same smoker. And want long cook with out having to mess with chunks or chips.
post #13 of 30
I think I see the problem.

I suspect the combustion gasses from the burner have depleted the oxygen and the way the side mailbox is laid out, the hot oxygen starved gas is flowing up and out what would be the fresh air intake holes for the mailbox mod. In essence those holes are acting as exhaust ports and you don't really have a source of fresh air for the pellets, chips, etc.... The blackend and unburned chips is another sign of this (like DaveOmak said, you are making charcoal which is formed by heat in an oxygen starved environment. Here is what I'm talking about:

I think the solution would be to block the existing air inlet holes as they are too high and are functioning as an exhaust. And then add new air inlet holes towards the bottom of the side smoke box. I would also block most of that large opening between the two boxes leaving just a small area at the top open. Now your air flow will be into the side smoke box from the new inlets, over the smoke tray and up into the smoker main body. Any hot gas from combustion will naturally want to rise and since there is no longer a "exhaust" at the top of the side box, the natural flow would be to stay in the main smoker body. The chimney effect of the main body and the rising hot gas will also help "draw" fresh air in over the smoke chips/pellets and into the main chamber and food area.

It would work like this:

Before cutting new holes and permanently blocking old ones, I would try the theory using something like wads of foil to plug the existing side smoke box holes. You can leave the door open as in the photo and use foil to block all but a opening at the bottom to simulate the new air inlet holes, and then use foil or a piece of sheet metal held in place with the side box bolts to block all but an opening at the top of the hole between the side smoke box and main chamber. That way you can test if this works before cutting anything.

Something like this:

post #14 of 30
Thread Starter 
Your pics aren't working. Also the only time I have had with chips and or chunks turning black is why before I did any mods and used the stock chip pan and also used a cast iron pan as well. When I burn pellets in the side box they burn up to ash no problem.
post #15 of 30
Thread Starter 
If I could cold smoke everything I would be set. Took this stove cover and placed it over burner and have great smoke with the two holes in side of added box.

post #16 of 30

I think that pretty much confirms my theory the holes near the top of the side smoke box are too high and are acting like a exhaust vent with heat from the burner.  It works fine when there is no heat from the burner as indicated in your last post.


Are the photos with the air flow notes still not loading?  I see them (anybody else see them?).

post #17 of 30
Thread Starter 
If the two holes were acting like a exhaust wouldn't they be having smoke go out of they? Whould it be better to have holes on the bottom under amnps?
post #18 of 30

Not necessarily.  In an oxygen starved state, there might not be much smoke to start with.   Take a couple of pieces of foil and try the low air intake test with those upper hole blocked (as in the 3rd photo).  That's about the only way to know for sure.

post #19 of 30
Thread Starter 
Can't see pics sorry could you email them
post #20 of 30

I use the AMNTS tube smoker in my GOSM, and have no problems getting it to smoke properly. One thing that I see different with your setup is that you have gasketed the door. I have never done that so I have tons of outside air mixing in all the time. I think that sometimes air tight is not a good thing, especially when burning propane. I would recommend making the modifications that Dave mentioned above to your side box that holds your AMNPS.

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