New OK Joe Longhorn 3-1 project with mods

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Fire Starter
Original poster
Sep 16, 2010
Salem, Oregon
This thread will be for my new purchase, an Oklahoma Joe's Longhorn 3-1 Combo. I will be posting mods and improvements as they get done.

The Oklahoma Joe Longhorn 3-1 is half propane grill, half smoker, with a side firebox and a side burner. The smoker cook chamber is approx 20" dia x 20" long, and the side firebox is approx 19 1/4" dia x 17" long. Initial quality seems decent, its a heavy duty build. Purchased from Lowes for $429.

Decided to do several mods during initial assembly to start off right. I assume that temps at firebox seams will be higher than 500 deg F so I used a black wood stove cement rated at 2000 deg F max (purchased from local fireplace retailer), to seal between the two halves of the firebox, and between the firebox and cook chamber. I also spread it with my finger along all of the interior seams in the firebox and cook chamber. I used a light to hold on the inside while looking through the seams to verify that I had sealed everywhere. After initial burn, this material hardened to a rigid state, and anywhere that it was thin is already peeling.

I sealed around the firebox door, cook chamber door, and exhaust pipe with black rtv food grade silicone (Amazon) 500 deg F max. There were quite a few gaps between the backing strips and the doors, so I added more silicone where I thought it needed. I spread shortening by finger on the back of the door, so once silicone was set up, the doors opened and the silicone was left with a pretty good seal. Saw very few smoke leaks during initial burn.

Baffle and tuning plates - I had some 1/4" thick flat bar scraps around, so I welded two together to make the baffle, and just cut two 4" wide bars to length - they just sit in the cook chamber. I can adjust my gaps as needed.

I wanted to seal as many cracks as possible to control air flow. The fresh air damper was pretty tight, but the gap around the door added quite a bit of a leak point. I purchased some fiberglass tape from a local fireplace company. It is approx 1/8-3/16" thick x 3/4" wide. I could only apply it where it wouldn't get in the way of the door closing, the damper movement, and the ash cleanout along the bottom.

I was able to use the charcoal basket I had from my previous smoker. It has two steel plates to give me a small version of the minion burn method, so I can burn around in a U shape.

Mods still to come:
Add a silicone seal for thermometer probes to enter the cook chamber:

Purchase and install the Lavalock automatic blower with probes:

Build a different handle system to lift the end of the whole unit. It is over 200 pounds, and the designated lift point is the handle on the end of the firebox. Everytime you lift there, you flex the steel sheet material at the joint between firebox and cook chamber - NOT GOOD. I intend to design and fabricate something that will allow lifting from the frame below.

Air flow mystery from initial burn. Couldn't get cook chamber temp above about 220. This is normally fine for low and slow cooks, but not good if that is the max and if the fire is not drafting properly.

When putting the measurements into the Feldon calculator, it is quickly apparent that the firebox is way too big. 248% of the recommended size. The fresh air inlet is way too small. Calculator recommends 15.62 sq in, I estimate this one at about 9 sq in. Exhaust is too short - calculator recommends a 3" exhaust to be 36.86 inches, original pipe is about 7" long from top of cook chamber. If you add the vertical distance from the actual bed of coals to the top of the cook chamber you still come up very short. Calculator recommendation for opening between firebox and cook chamber is 41.66 sq in. Original measures about 57 sq in. So it makes sense to me, that heat is trapped in firebox and not drafting or moving properly through.

I wanted to install the Lavalock automatic blower anyway, so I am hoping that this will force air through. If I have to reduce the firebox volume, I think I can relatively easy by adding a plate at the bottom, but I am hoping to not have to.

I would appreciate any tips, especially on air flow.

Pics here:
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I lined my fire box with fire place bricks. That brought my basket up a little higher closer to the opening to the cooking chamber. Also helps in retaining heat and one day burning out the bottom. I own a Highland but seems they have the same quality issues with the other styles. Same issues with heat transfer. I have to keep my door open some on the fire box as the intake is too small. I bought a blower also but have yet to use it. I keep my stack wide open then cut back to about 3/4 sometimes half close once it gets going. Haven't added onto the stack length yet. Most do. I added bread pan on the inside at the exhaust pipe and cut it down to where the opening is just at grate level. That helped in bringing the heat back down to the grate level. Looks like a really nice unit you bought. Good luck with everything.
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Got a probe grommet installed today. Drilling through the end metal on the Longhorn with a step drill bit was quite a chore. I won't do that again if I can help it. It did prove one good thing to me, that the metal is quite thick on these units. It would estimate it to be about 12 gauge which is just under 1/8" thick, and that is pretty heavy duty. If I have to do it again, I will try a bi-metal hole saw. Anyway, I got it in and it worked great. These were ordered from Amazon - I would post the link but forum website appears to not like that...?

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