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Horizonal Offset Smoker Mods

Discussion in 'Charcoal Smokers' started by ddave, Mar 29, 2009.

  1. ddave

    ddave Master of the Pit OTBS Member SMF Premier Member

    Horizontal Offset Smoker Modifications

    For a lot of new people just starting out, their first smoker is a horizontal offset smoker with side firebox. While many of the horizontal offsets work great with no modifications, most of the entry-level ones that new smokers first get, such as the Brinkmann Smoke N Pit, the Char Broil Silver Smoker and the Char-Griller Smokin’ Pro, to name a few, can benefit from a few simple and relatively inexpensive modifications. These modifications will help create more even distribution of heat and smoke, make it easier to maintain and control temperature, give you more accurate information regarding the temperature of the smoking chamber, and generally make your early smoking experiences much more pleasant.

    Rest assured that I am not the first person to invent these modifications or discover their usefulness, Collectively, most of this information is available on the forum but it is sort of piecemeal and in various threads. I am just compiling the information that I have found in a single thead in the hope that it will save others some of the frustration that I experienced starting out. There are a variety of designs and materials that can be used for these modifications; I am just illustrating the ones that worked for me on my particular smoker, which is a Smoke N Pit.

    These modifications include, in no particular order:
    · Thermometers
    · Chimney Extension
    · Baffle
    · Tuning Plates
    · Charcoal Basket


    The thermometers that come with these units are usually not very accurate, and they are usually not mounted anywhere near grate level. Often times they don’t even have numbers on them, just the words WARM, IDEAL, and HOT.

    For more information on what IDEAL can be on one of these thermos, read this thread.

    Also, there is usually only one in the center of the chamber. Sometimes the temperature difference from one end to the other can be quite significant. That is useful information to have so you’ll want to have two thermometers mounted at grate level, one at each end of the smoker.

    You want to measure the temperature of the smoking chamber at grate level because that’s where the meat is. I used analog dial thermometers with a 3” face and 3” stems. I think the stems are a little short though and if I had to do it over again, I would get dial thermos with 4” stems.

    Although it is good to have the analog dial thermos it is an even better idea to use digital oven thermos. You can push the probes through a potato hunk or block of wood and place them on the grate.

    The nice thing about the digitals is that you can set alarms to notify you if the temperature gets too high. Some models even allow you to set a low temp alarm as well.

    Make sure you “boil test” the thermometers every once in awhile though. This entails inserting the probe tip in boiling water and noting the temperature. Depending on your altitude, the thermometer should read darn close to 212° when the probe is in boiling water.

    Chimney Extension

    Most of the entry level models have the chimney hole cut in the top of the smoker and the chimney does not protrude into the smoke chamber at all.. Heat and smoke rise so what happens is the heat from the firebox rises, runs along the top of the lid on the way to the chimney, and exits the smoker without doing much at grate level. Since the meat is on the grates, we would like to encourage the heat and smoke to travel across the meat on their way to the chimney. This helps to even out the temperature across the grate and makes the smoker more efficient. To accommodate this, it is a good idea to extend the chimney down to close to grate level. There are several different ways to do this. One is to use dryer vent ducting. Another is to roll up some aluminum flashing, place it inside the chimney, let it unroll and let friction hold it there. I chose to use exhaust tubing.

    I took my lid out to the local muffler shop and had the guy cut a piece to fit and he “swedged” it so that it would stay in place when pushed up inside the chimney.

    As you can see, it is pretty close to the level of the grate when the lid is


    A baffle is a “deflector” of sorts that is placed at the firebox end of the smoker at the point where the firebox opens into the smoke chamber. The purpose of the baffle is to protect the meat at the firebox end from extreme heat and help the heat travel farther down the smoke chamber to even temps out a little bit. Again, there are a few different ways to do this. Some people use cookie sheets, some just use a large foil roasting pan filled with water placed against the opening. I uses a piece of 1/8” steel, cut to fit so that it lays at about a 45° angle and the bottom is about 2-3/4” inches from the bottom of the smoker.

    You will need to assess your smoker for the proper size. Making a template out of cardboard is helpful.

    Tuning Plates

    Tuning plates are usually pieces of steel laid across the bottom of the smoke chamber. They are of varying widths and are placed side by side in such a way as to leave gaps of various widths between them. The idea is to get the heat from the firebox to travel farther down the smoke chamber towards the chimney end. The placement of the plates and the size of the gaps can be adjusted to “tune” the smoke chamber temperature wise.

    Again, there are various ways to do this but I used plates of 1/8” steel of 10”, 8”, and 6” widths. You will want them long enough to lay in the bottom of the smoker yet sitting high enough to be just above the bottom of the tuning plate.

    Some people put “rails” of 1/8” x 3/4” flat bar for the plates to rest on. Again, you will have to assess the width and length of your smoker to come up with the appropriate sizes. Again, making templates out of cardboard are helpful.

    Another twist on the tuning plate idea is to have a plate that runs the length of the smoker with rows of holes of increasing size -- smaller at the firebox end and larger at the chimney end. The idea again is to move the heat farther down the smoking chamber to even out the temperature. I believe Horizon smokers use this set up and they call it a "Convection Plate".

    Here is a diagram that I drew for a convection plate for my smoker.

    Some folks have done things along this line and reported good results. I have not gotten around to having one made yet, but when I do, I will test it and post the results.

    Charcoal Basket

    Solar has a great thread on making the charcoal basket.


    Hopefully you found this information useful and if anyone has any corrections or additions to make, please feel free.

    jack3608, paddedroom, button and 12 others like this.
  2. bwsmith_2000

    bwsmith_2000 Master of the Pit OTBS Member

    Great job! It's good to see all this brought together in one spot. I have a Silver Smoker and could not believe the improvement as a result of the modifications. I don't remember all who posted the various mods but I certainly appreciated and thank them. If there are those who have an offset smoker like the ones Dave has mentioned and haven't done the mods, I'd highly recommend doing them before your next smoke. You won't believe how much better the smoker will perform. Points to you Dave.
    stevetn likes this.
  3. meat hunter

    meat hunter Master of the Pit SMF Premier Member

    DDave. Great post. I was just discussing a few point with sumosmoke about the offset I am making right now. About the chimney. I have seen both ways to mount these. Flush with the top and extended down to grate level. My question for you is, when the chimney is down at grate level, would this not let allot of smoke build up? Or is there sufficient air flow to move into the chimney? What is your take on a flush mounted chimney with a baffle adjustment in the stack? Would that offer more control?

    Also, one thing I have yet to find on here and maybe you can answer. Does the length of the chimney outside matter? I've seen some that appear to be only a foot or so and others about 3 or 4 feet.
  4. azrocker

    azrocker Smoking Fanatic SMF Premier Member

    Here is a work book zipped. Not sure where I got it but it came from a smoker site. If this belongs to someone here let me know so I can give credit where credit is deserved! I like mine tall so I don't stand in the smoke. I can also turn the elbow on the top to adjust so the wind does not blow in my stack. I am actually thinking of raising it and adding another.
  5. rickw

    rickw Master of the Pit OTBS Member

  6. azrocker

    azrocker Smoking Fanatic SMF Premier Member

    Thanks! I had saved it but did not add credit! I do want to credit this guy because this simple workbook is ingenious
  7. ddave

    ddave Master of the Pit OTBS Member SMF Premier Member

    Thanks for the nice comments, guys.

    Looks like that spreadsheet is a good resource for anyone building a smoker.

    I would think that as long as the chimney is not obstructed there should be plenty of airflow to keep the smoke moving. An inch or so above the grate seems to work in these inexpensive offsets. Some of the more expensive models have a baffle adjustment in the stack but I have been told by many experienced smokers to keep the stack wide open anytime you are cooking. Use the intake to regulate heat -- not the exhaust.

    I think the length of the chimney outside does matter. There is going to be a certain amount of loss of velocity of air as it moves up a taller chimeny. Since warm air rises, it will want to go up the chimney but as the air cools, it becomes heavier and will at some point impede the flow. This will also be the case if there are bends in the chimney. My physics are a little rusty so I cannot tell you exactly where this will happen but there will certainly be diminishing returns as the chimney length gets longer.

    Other people have mentioned this with the UDS. Some people want to "trick it out" with tall chrome stacks which look cool, but then they notice that they can't keep the temp up anymore because there is insufficient draft to keep the fire going.

    Hope this helps.

  8. tasunkawitko

    tasunkawitko Master of the Pit OTBS Member

    thanks for the ideas and the suggestions!
  9. meat hunter

    meat hunter Master of the Pit SMF Premier Member

    DDave, azrocker and RickW. Thanks for your input. I checked out the links, but I run a MAC. Could not view the excel spreadsheets. I just have to find an appication that will open them. Lots of good ideas from lots of folks here. Couple more weeks and I'll have my smoker going, I can't wait. I have officially retired the "Big Chief".
  10. tasunkawitko

    tasunkawitko Master of the Pit OTBS Member

    that big chief should still work great for cool-smoking fish and cheese, bud!
  11. ddave

    ddave Master of the Pit OTBS Member SMF Premier Member


    Well . . . I guess we can let that slide.[​IMG] You're here so you can't be all bad. [​IMG]

    Just kidding. Let's not get a PC vs MAC war going now.

    Here you go.


    Reads and writes all MS Office file types and is available for MAC OSX Intel and PPC.

    And, it's free.

  12. azrocker

    azrocker Smoking Fanatic SMF Premier Member

    I have saved a version in open office if you are interested. I changed it to their format as that is what I run. Don't like Billware so I have ubuntu on my laptop. My desktop came with Vista so I left it on.
  13. jjmrascal

    jjmrascal Smoke Blower

    DDave and whoever else,

    I know I am responding to a month old posting, but I have been mulling some smoker mods on my OK Joe for several years. I am now getting ready to do one thing or another. I really like your post covering all the classic methods.

    I recently got a 2'x4' sheet of scrap 1/4" steel from the scrap sales at work. I had thought of the convection plate, then making it a reverse flow, but I have been thinking the simplest is tuning plates. I don't have access to a welder so it would be me, a reciprocating saw and several blades doing the work.
    1. Is there a particular distance below the meat grate the plates need to be?
    2. Does the deflector lip need to extend below the level of the plates, or just at the same level?
  14. ddave

    ddave Master of the Pit OTBS Member SMF Premier Member

    Well, I am not an engineer so this is just my opinion.[​IMG]

    Mine are about 5" below the grates, but I think my plates are actually too low. I think I am close to restricting the area too much. If I had to do it over again, I would shoot for making them even with somewhere close to the halfway point of the cut out from the firebox -- maybe a little higher. You don't want to block the heat too much, just move it farther down the chamber. But make sure that if you use a water or sand pan in your smoker (I do from time to time) that you leave enough room between the meat grate and your tuning plates to set the pan on.

    I would make the deflector lip of the baffle even with the bottom of the tuning plates.

    Again, I have no engineering expertise to back this advice up with, just my hunch and knowledge of what worked for me.

  15. jjmrascal

    jjmrascal Smoke Blower

    Caveat duly noted. Thanks for the help and I will let you know how it goes or be back with more questions.[​IMG]

  16. big_z

    big_z Newbie

    Thanks for this post. the pics are very helpful. I've read about these mods elsewhere but this post is much more concise and helpful.
  17. big_z

    big_z Newbie

    I found a 3" elbow at Lowes I"m thinking of using to drop my smokestack down to the grate. would there be a problem having a curve in the pipe right above the grate?

    also i've seen some mention of people placing pans under the smokestack opening. What is the purpose of this?

  18. ddave

    ddave Master of the Pit OTBS Member SMF Premier Member

    I think a straight extension would work better.

    I have no idea. I have placed a pan full of sand at the smokestack end but it was on the tuning plates under the cook grate to act as a heat sink and help stabilize the temp at the far end. I can't think of any reason you would want a pan under the stack above the cook grate though. Seems like it would interfere with draft.

  19. billbo

    billbo Master of the Pit OTBS Member

    Bump! Wow, how is this not a stick? All the mods are outlined here perfectly. One problem is the link Ddave posted from Solar about the firebox is not working for me. Can anybody help with that?
  20. eaglewing

    eaglewing Smoking Fanatic SMF Premier Member

    Some of those LINKS he has in the original need updating, or it's just me but they don't open to a thread...

    I wana see that Charcoal Basket thread....