Need help sealing a firebox door on an offset smoker

Discussion in 'Charcoal Smokers' started by gartlesby, Aug 26, 2014.

  1. gartlesby

    gartlesby Newbie

    Howdy guys and gals,

    I recently got a new offset smoker and in my burn in tests I am having a hell of a time controlling oxygen to the fire. With everything closed up, the temp inside the pit near the firebox was reaching over 500 degrees, after 1 hour! (perfect example of why you should do test burns to learn your pits!) I know there's a lot I can do to make improvements in general to the offset smoker:

    - seal lids on firebox and pit

    - seal any seams that aren't welded

    - seal firebox connection to the pit

    - baffle inside the pit to direct heat down and to the other side of the pit

    - lower the chimney to the grate

    - wrap in welding blankets

    - seal 'other' leaks in my firebox

    It's the 'other' leaks that I'm needing help with. Here are some pics to explain:

    This is my firebox door - there is about a 1/4"+ gap between the door and the firebox itself:


    Here is the catch for the door latch - this hole is huge! No wonder the fire was raging even with everything closed up:


    How would you guys suggest I fix the door gap? For the latch hole I was thinking I could just use silicone and a small metal square to seal it from the inside, but the gap around the door is confounding me. I don't have a welder or know how to weld, but I'd love the chance to learn. If I can fix this in a simpler or quicker way I'd rather go that route so I can get smoking on this bad boy faster - it's much bigger than the weber kettle I'm coming from!

    Thanks for your help,


    edited to add a couple more questions:

    1. The silicone recommended by Amazing Ribs is only rated to 500 degrees - is that good enough?

    2. Hardware store guy said JB Weld wasn't good enough since things would be getting too hot - but this was also recommended as a sealant/glue by Amazing Ribs. Should I not use it?
    Last edited: Aug 26, 2014
  2. sqwib

    sqwib Smoking Guru OTBS Member

    I can pretty much guarantee that your temp problem is not from the gap in your door, I sometimes run with my door open a few inches with no problems.

    The firebox does not need to be airtight.

    I would look in other areas to rectify this problem, here's a few to start
    • Fire Management
    • Check thermos.
    • Baffles
    • Tuning Plates
    • Add thermal Mass
    • Diffuser at the inlet area of the firebox
    • Baffle where the heat pounds the first point of contact.
  3. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Pop rivet or bolt a flange on the inside of the gaps, or the outside would do... to seal the FB..... The metal does not need to be thick... 26 gauge would do nicely.. all you are doing is sealing air "out"...
  4. radioguy

    radioguy Smoking Fanatic

    Daves suggestion is the way to go. You can buy pre-cut metal at your local home improvement store. Flat bar is available in a variety of sizes. Drilll holes, pop rivet,bolt,self tap sheet metal screws.

  5. gartlesby

    gartlesby Newbie

    I was using freshly calibrated digital thermometers to gauge the close and far ends of the pit. I'm surprised you're saying the temp problem is not due to the airflow - on my little weber kettle adjusting the air intake to the coals was the biggest influence on controlling the temperature.

    What do you mean about Fire Management? I have used the minion method successfully for quite a while, though I'm certainly not an expert.

    As I understand it, baffles, tuning plates, thermal mass and the difuser would help with evening out the temerature, but I don't understand how that would keep my coals under control in the first place.

    Thanks for the feedback.
  6. gartlesby

    gartlesby Newbie

    When I was there looking for metal I only saw things in the size of 2'x4' sheets or larger. Can I cut 26 guage with tinsnips or something?
  7. gartlesby

    gartlesby Newbie

    Thanks for the pointer - I'd be worried about the flange warping over time which is why I was thinking something thicker, but again I don't really know anything about fabrication like this so I appreciate the tips.
  8. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Yes you can cut it with tin snips...... Also, warping has nothing to do with the thickness of a metal.... the expansion factor, of a given alloy, determines how it expands.. .. Roofing sheet metal is about 26-28 gauge... or something close....

    Also, there are rolls of sheet metal in the roofing department.... don't get galvanized... get painted... it is a "baked on finish" that is fairly heat resistant and doesn't give off toxic fumes like galvanized does....

    OR, in the hardware section are metal displays that have thicker hot and cold rolled steel.... like 1/8" x 1" strips.... take your pick...
  9. jburn244

    jburn244 Fire Starter

    The firebox certainly doesn't need to be airtight as mentioned. Based on the photos I don't see how you'd be getting 500 degrees in the cook chamber unless you had the firebox filled to the brim with fuel. 

    What kind of cooker is it? How are you bringing the pit up to temp...Minion method? How much lit vs unlit are you starting with? Lump/briquetts? Split logs for wood, or chunks?

    Enjoy your new toy...figuring it out is part of the fun!
  10. sqwib

    sqwib Smoking Guru OTBS Member

    It seems you are convinced that it's the coals and that its the oxygen to the coals creating too much heat, if that's true do a simple test, shut down your intake in increments wait 10 or 15 minutes and see what happens, see if there is a significant difference in temps

    I could have suggested a fix for your firebox but I don't believe that's the problem.

    My pit had a 75° difference, after I baffled it the temps were fairly even across, from what little info you posted I am guessing you are getting a hot spot... did you check the temp on the other side away from the firebox?

    how are you gauging the heat... in the direct path of the heat.

    Charcoal needs little oxygen to burn... less than wood, now unless you have a nasty draft blowing on your coals I would say more is going on here, from the pics you showed, those gaps and the little opening where the latch is should not be a problem.
  11. sqwib

    sqwib Smoking Guru OTBS Member

    Post some pics of the entire smoker, inside and out.

    I don't want to put you on a wild goose chase with suggestions.
  12. grillmonkey

    grillmonkey Smoking Fanatic

    I agree with SQWIB, I don't think the problem is the firebox.

    I couldn't get 500 degrees in my offset smoker's cooking chamber if I left the firebox door wide open with a normal amount of wood or charcoal. Maybe if i filled it up with wood...I would say maybe hot on the cooking grate just outside the firebox, but not across the whole cooking chamber. I'm sure all you need is a deflector to direct the heat from the firebox to the bottom of the cook chamber, and some tuning plates.

    The deflector directs heat under the tuning plate. It's just a scrap piece of stainless steel I had. You could use a cookie sheet and tin snips to cut it. I just used one of the existing firebox bolts to hold it in place.

    The tuning plates are from a piece of 3/8" aluminum I had laying around. I cut each piece progressively narrower with a metal cutting blade on a circular saw. Widest piece nearest the firebox.

    Any metal shop will cut you some tuning plates to your specs.
  13. gartlesby

    gartlesby Newbie

    Ah I probably used the wrong word there - I just meant deformed after repeated pressing up against the box over time.
  14. gartlesby

    gartlesby Newbie

    This is the smoker I got:

    But it's a 'classic' I think - it doesn't have wood shelf or handles, it has a metal shelf and spring handles. Otherwise the same I believe. Regarding air-tight firebox - alrighty I'll take y'alls word for it, I was making an assumption based on my experience with my weber kettle, the slightest variations in the bottom vent could bring my temps up and down really reliably.

    I'm starting with about a chimney worth of unlit charcoal and then I start 4-5 briquettes until ashy all over. I drop them on top of the unlit and kinda poke them apart. A main reason that I suspected the air flow as the problem was because in my webber I could restrict air enough such that the coals would only ever smolder and get ashy, but in this firebox, they were glowing in the middle and had flickers of flames which I could not extinguish by closing things up.
    Last edited: Aug 26, 2014
  15. gartlesby

    gartlesby Newbie

    Thanks again for your help.
  16. gartlesby

    gartlesby Newbie

    Thanks for your feedback to - I was planning on doing all these things but I thought I had to get something done about the firebox first. Y'all have convinced me before I get all crazy with the firebox I'll do the baffle and tuning plates stuff and see how things read. 

    This kind of great help is why I came to the pros! Thanks again yall.
  17. jckdanls 07

    jckdanls 07 Master of the Pit Group Lead OTBS Member

    I would do the "sealing up deal" ,,, if not doing anything but putting your mind at ease... Do you own a hand held grinder ? If so, buy a cutting blade for it to cut a little bit thicker metal (instead of roof flashing) to do the door seal... and then do the hi-heat silicone deal where you put a bead on the new seal and cover with saran wrap.. close door and latch it and leave over night... and then do the patch behind the door latch catch... that will be a start ...
  18. sqwib

    sqwib Smoking Guru OTBS Member

    Last edited: Aug 27, 2014
  19. gartlesby

    gartlesby Newbie

    Hey yall,

    Regarding the baffle and tuning plates, I'm finding a lot of info about why I should do them - but having trouble with the 'how'. I had some 6", 4", 3" steel plates fabricated from a shop nearby, and I plan to use these for tuning the pit. My confusion is how the baffle is supposed to work. The Hondo is a barrel-style rounded pit, so it's not as easy as cutting a plate to size and then putting it over the firebox hole - can I use some of the aluminum flashing cut to size? If I don't use the flashing, can I use a bit 12"x12" steel plate to direct the heat under my tuning plates? The big plate wont create a seal along the sides, so I'd be afraid it would be pointless.

    Thanks again for the help.

  20. grillmonkey

    grillmonkey Smoking Fanatic

    Some people use a cookie sheet to deflect the smoke/heat under the tuning plates. I had a piece of stainless that I cut with sheet metal shears. Then used one of the firebox bolts to hold it in place:


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