When you open the choke up and the burners are burning more efficiently you will need to turn down the pressure as you will get more heat with less gas and so the tanks will last longer.

So the burner tops need to be very open?

That depends and you haven't given enough information to accurately answer your question.

Sorry. I have noticed you guys call them the chokes. Those should be pretty much wide open?

It depends on the burner and what forge atmosphere you are trying to achieve.  This is sort of like "I have windows in my house---should they be open or closed?"

Start opening them till the flame is tuned. You'll get the best heat with a neutral flame but SLIGHTLY rich is okay to minimize the chance of scale formation. The flame current within the forge chamber can draw ambient air in through the doorways and cause zones of oxidizing atmosphere in the chamber. If a neutral or carburizing atmosphere is important a SLIGHTLY reducing flame may be called for. 

Open the chokes a LITTLE and check the results. One change and test before the next change. 

Frosty The Lucky.

I have a 1" liner. It leaves a space that is 5"h, 5"w, and 10"L. The back end is closed off and ive been running just the back burner with the front one closed off. There are two burners pointing directly down in line. After tuning to the best of my ability i can get nice orange steel but cant reach weld temp. i am unsure what more info is needed. Any tips to boost the heat would be helpful.  I tried to put a door on the front but the flames were escaping through the top so i scrapped it. Its a cheap amazon burner, might build scratch but i got some learning to do first.

1" of what? I don't recall if you said already, my  memory is spotty on a good day. That is only 250 cu/in volume. Two 1/2" burners would make it a SCREAMING HOT forge even with a less than optimum liner. You need to think of forge size as the volume of the chamber, not the dimensions. It's the volume that determines size number of burners, The shape is the main factor in number and placement.

One 3/4" burner is more than necessary but not so much as to be a bad thing. Running it on the rear burner wouldn't be my choice unless I wanted the temperature differential. I tend to like having a hot spot so I can better control the hot area on the work but like it within reach (front) so I'm not getting the whole piece hot to set a rivet, etc. 

Frosty The Lucky.

It is a 1 inch thick ceramic blanket that came with the forge and refractory mix. I was using the back burner because of the way it came built. Sat awkward, Fire pointing at propane, and a valve between burners that only allows either two or the one but not one or the other. Ill get a picture hopefully i make some sort of sense. 300 cu" inside. Definetly some heat going up the burners..

Turn the burners around so you can turn the back burner off instead. Move the propane line and or tank so they aren't in the flame. 

I can't say I see much I like about those burners, it probably takes both to hope for welding heat in 300 cu/in. It'll do for a learning forge anyway, you can build better once you get into the craft a little and know what you need/want for the next one. We'll get this one reasonably hot so you can get to work in it.

Frosty The Lucky.

Got it pretty hot today nice high orange steel. I would like to at least be able to surpass liquid copper temperature. Someone had asked why i wanted welding temp and the reason for that is i would like to attempt some canister demascus... Eventually. Should i encase it in bricks and mortar? And yeah if i had to pick one issue it would be the cheap burners.

3 hours ago, Frosty said:

Turn the burners around so you can turn the back burner off instead. Move the propane line and or tank so they aren't in the flame. 

Feeling dumb. Did not think of the easy solution: pull the burners spin forge insert burners

Ahhhh, my day is complete! 

Welcome to the club, it's a familiar feeling for all of us. Just wait till some 8 year old asks, "Why don't you . . .?" and you stand there with your mouth open rhythmically slapping your forehead. 

Moments to be treasured.

Frosty The Lucky.

That’s why I don’t let 8-year-olds into my shop. 

4 hours ago, Frosty said:

can't say I see much I like about those burners

Agreed; those burnera were built to look nice--not to work nice.

You're missing out on a LOT of good ideas you'll never think of yourself, John. 

Frosty The Lucky.

Got some great heat out of it today. Liquified some copper and did some bad forging on my first knife. Should have taken a picture of the "crucible" before i used it but it was an afterthought.