Mailbox style mod on BBQgrillware smoker using an ammo box. Smoke flow problem resolved!

Discussion in 'Propane Smokers' started by cali-q, Jul 7, 2014.

  1. I hope I am posting this in the right place. 

    I attached an old ammo can to the side of my smoker to use with my AMNPS.  I connected it directly into the smoker without the long hose  that is often seen on the mailbox mods.  The smoke flows great rising out the vent at the top when there is no heat turned on in the smoker.  If I turn on any heat in the smoker, the hot air comes flowing from the smoker into the ammo box and pushes the smoke out through the box.  The moment I close the door all the smoke is being pushed out the vent holes in the ammo box.

    In case it matters, I have three vent holes in the bottom on the ammo box and three in the door at 3/8 inch each. 

    This particular smoker has a vent at  top.  I tried rigging a long stack to see if that made a difference, but it didnt appear to change anything.  I am hoping someone might have some suggestions on what to try.

    I have tried it with both with and without the chip tray.  

    Thanks in advance for any suggestions

    Last edited: Jul 11, 2014
  2. mneeley490

    mneeley490 Master of the Pit OTBS Member

    Heat rises. I like the ammo box, but I think you need to put your box lower than the burner. That will mean a bit of hose.
  3. Thanks for the reply mneeley.  I thought I had seen some builds similar to mine.  I was hoping that I had missed something small. Back to the drawing board I guess.
  4. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Cali, morning...... I'm guessing here..... When the burner is on, it is raising the temp of the air in the smoker..... Heating air causes it to expand..... Maybe, you need more exhaust area for the expanded air to escape the smoker body allowing more air make up from the ammo can....

    Start by drilling holes in the upper part of the side walls of the smoker body.... I would use a step drill.... it works better in sheet metal.... As you drill holes, (I would start with 1/2 - 3/4" holes), the smoke "should" start moving from the ammo can into the smoker body and out the exhaust..... Don't worry about too much exhaust... Good air flow and thin smoke make for great smoked food.....

    Also, most gas fired smokers have a burner that is too big for the smokers that come from the factory.... they add a water pan to "suck up" the BTU's from too large a burner..... Some folks have used a needle valve and lower pressure regulator to get the BTU's to a 'manageable" level and lower temps so a water pan is then not necessary to get smoker temps to the low 100's degree range.....

    Now about the burner.... most burners have a specific design to burn the fuel.... to get a lower BTU output, you may need to plug some of the holes in the burner ring to get a good flame... One material that should work to plug some of the holes in the burner ring is furnace cement or fireplace mortar (the kind in a can or tube, not the stuff you mix in a cement mixer).... It cures very hard when the high temp is applied..... it has an odor for a few firings.... start by plugging 10% of the holes in the burner and increase until you see a very nice flame, with no yellow, emitting from the burner holes.... This will take some experimenting to achieve the "clean blue flame" that is about 1/2-5/8' long... also check the smoker temp during this process...... I know it sounds like a lot of BS and work.... but.... getting to the point where the smoker works extremely well will be worth the process...

    I'm trying to cover all the bases here.... Really hard to hit the nail on the head from the desk....

    It is very unfortunate that manufacturers don't have a clue on "how to build an off the shelf smoker" that works..... They think a smoker should get to 350 deg. and ignore the "smoke temp. zone" of 70-160 deg. F.....

    That's my opinion.......


    Something similar to this should work....
    Last edited: Jul 8, 2014
  5. Dave thank you for the detail response.  I will start off with the additional venting and starting  fixing the other stuff from there. As this is a hand me down I dont have a lot of concern about drilling a couple holes in the cabinet. I already purchased a needle valve and gas line setup, but I have not gotten around to buying the hardware to make it work with this smoker.  The current connectors are on the small side and my local Home Depot does not have a good selection of brass fittings.  

    I have been trying to resolve some issues with the burner and I will try out your suggestions.  I am having a tough time getting a nice blue flame in all but the very lowest setting. If I turn it up even 1/2 way (which is about where it will run at 225 with a large water pan) I start getting a lot of yellow flame.  I have to admit I haven't gotten around to researching this on the forums, but I did try to make sure I got everything cleaned out before lighting her up for the first time.  

    Thanks for all the help.  
  6. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    A yellow flame is lack of oxygen..... does the burner have adjustable air inlets.... like slide plates or a rotating plate on the end of the burner....
  7. No unfortunately is does not I will post some pics from the burner. Air inlets are just a screen on either side of the pipe that feeds into the burner itself.

    Underside of smoker

    Set to high

    Set to 1/2

    Turned all the way down
  8. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    I think Mneely has a good point..... the ammo can could be acting as a chimney...
  9. Thanks again Mneely and Dave

    I will give it a shot.  Should I enlarge the hole to 3" so that I can fine tubeing.  If so, what is the best way to do that?  Maybe a jig saw?
  10. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Best way to cut that hole...... PLASMA..... convince SWMBO you need a $2000 plasma... :biggrin:
  11. Don't I wish!  I guess I will be pulling out the jig saw and doing a little tinkering.[​IMG]

    Good thing I got this smoker for free!
  12. Well I dropped the chamber down below the burning and it took off like a champ smoking away.  Thanks for the pointers Mneeley and Dave
  13. Here is the smoker with the box dropped down and some plumbing added.  Cold smoking a little cheddar and pepper jack.

  14. dward51

    dward51 Master of the Pit OTBS Member

    You still have a oxygen starvation issue with the burner on medium and high.  That flame should not be yellow, it should be blue like on low.  You need to get more air into the mix that is going to the burner.  Check the screen for the air inlet in your burner tube.  I bet it has cobwebs inside partially restricting the air flow to the air/fuel mix.  You may have to disassemble the burner element.  One of the by products of burning LP is moisture.  I had a cast iron burner that had a yellow flame problem.  Screen was clear but I found the inside of the burner had started to rust and the interior was slowly flaking off in small sheets.  It was just enough to restrict the air flow and throw the mix off.

    I would bet you are also getting soot on your food with that yellow flame.
    Last edited: Jul 11, 2014
  15. I took the whole burner apart when I first picked up the unit after firing it in up and see the yellow flames for the first time.  I cleaned all the tubing out but thus far no improvement.  I am wondering if I can just find a replacement burner assembly.  Does anyone where I can get a whole new control etc?
  16. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    You might be able to find a "side burner", for a gas grill, at a big box store... or off of an old grill from your neighbor... If you find a burner..... one that is smaller might be a good place to start.... usually the burners that come with gas smokers put out too many BTU's and control below 250 is impossible without a water pan.... just a thought....

    Last edited: Jul 12, 2014
  17. Thanks Dave I appreciate the advice
    Last edited: Jul 26, 2014
  18. Well I fully disassembled the burner and cleaned it well.  I made sure the tube and air vents were clear. No rust inside etc.  After lighting it still was having the same problem with yellow flame.  So, I decided to replace the regulator and hose (the hose was starting to wear a bit anyway).  Still the same issue.  Does anyone have any additional ideas?  Would plugging some of the many holes on the burner improve performance?  Maybe drill some small holes in the tube to increase air flow?
    Last edited: Jul 26, 2014
  19. ps0303

    ps0303 Meat Mopper

    What if you installed a needle valve between the tank and the burner to regulate the gas flow?  This was you would open the regulator all the way up but the needle valve will determine how much gas is fed to the system.  I have one on my Masterforge and I'll tell you I don't have much of a flame to get that puppy to 225-250.

    I know people are saying it's an oxygen issue but when you took those pictures you had the door wide open so it had plenty of oxygen to feed from.
    Last edited: Jul 26, 2014

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