# 120 Gallon smoker build



## justintr34 (Feb 24, 2020)

Hey everyone,

Long time lurker first time poster. I made a fire box in high school while in welding school and never put it on a chamber. I now have a 120 gal propane tank that I have cut open and started to prepare. My question is whether or not I should build a new firebox or not. The firebox I already have built is 16.5" wide by 16.5 tall" and 20" long, which gives me 5,989 cubic inches. According to the calculations it says I need 9,240. I have never smoked meat before and have very little knowledge on the topic so im not sure how big of a deal it will be.


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## JC in GB (Feb 24, 2020)

There are threads on this forum that will give you the proper calculations for making your pit.

Are you making a conventional or reverse flow unit?  If your unit doesn't have the right air flow, you will have no end of problems.

It is well worth it to get everything measured and calculated first.

Happy smoking.....   

JC


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## smokin peachey (Feb 24, 2020)

If you want to use the 120 gallon tank you might wanna build a new bigger firebox. You also could use the fire box you have and cut the tank down some. 
Are you using Feltons calculator?


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## indaswamp (Feb 24, 2020)

I'm in the car along for the ride...


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## justintr34 (Feb 25, 2020)

Yeah I am using the calculator. That’s where I got my numbers from. I just didn’t wanna have to spend money on more steel plate if I didn’t need to.


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## JC in GB (Feb 25, 2020)

justintr34 said:


> Yeah I am using the calculator. That’s where I got my numbers from. I just didn’t wanna have to spend money on more steel plate if I didn’t need to.



It will be money well spent to get the proper fire box.  Looking forward to seeing pics of your build.

JC


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## kmmamm (Feb 25, 2020)

Alternatively, you could simply cut the 120gal tank down sizing it to the firebox.   Would be a whole lot faster and cheaper than building a new firebox.  Use it to learn,  if at some point you find the downsized smoker isn’t big enough,  you can always start a larger build from scratch.


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## dacolson (Apr 1, 2020)

Hate to see you cut down that 120 gal tank. What are the dims? 24" x 67"? That's a great size IMO. Look around for cutoffs or random steel on Craigslist of Facebook Marketplace. You'll be surprised how much you can find for cheap. Hang on to the firebox for another project. Like a vertical smoker!


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## justintr34 (Apr 19, 2020)

Like most people, life happens. Here we are so far though! Seems to be going well.


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## dacolson (Apr 19, 2020)

Looks great. You happy with the size of the FB?


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## justintr34 (May 2, 2020)

dacolson said:


> Looks great. You happy with the size of the FB?


Yeah I am! I did not use my old firebox. This is much bigger. 20” x 24”x 24”


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## justintr34 (May 2, 2020)

any advice on where to put the reverse flow plate? im not sure if it should just come right off of the top of the firebox or what? and then how much space do I want between the reverse flow plate and the cooking grate?


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## dacolson (May 2, 2020)

justintr34 said:


> any advice on where to put the reverse flow plate? im not sure if it should just come right off of the top of the firebox or what? and then how much space do I want between the reverse flow plate and the cooking grate?


I put mine right at the top of the opening between the FB and the CC.  About 7 or 8” off the bottom.


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## justintr34 (May 2, 2020)

dacolson said:


> I put mine right at the top of the opening between the FB and the CC.  About 7 or 8” off the bottom.


So right at the top of the firebox? How many inches higher is your grate from the reverse flow plate?


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## dacolson (May 3, 2020)

justintr34 said:


> So right at the top of the firebox? How many inches higher is your grate from the reverse flow plate?



yes. Right at the top of the FB. My grates are 3” above the RF plate.


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