Building headers can be challenging, and satisfying as well. As Pist-N-Broke stated, your first won't be your best, as evidenced by my first set over 55 years ago !
So here's a question. Do you start with the front port ,say number 1, then work your way back? Or do you start with the rear port?
I do start with the front port, and in some cases stack the pipe from the rear on top. Then, work the center two.
Yep, like Pist-n-broke said, the first set usually looks it. My first set was a 409 in a '55 Chevy and they were not pretty, a million little pieces to get around the A-arms, steering box, clutch linkage. My second set looked pretty good, I thought, until a real header builder saw them and pointed out all the mistakes. That radius tool is great. Cutting the bends on a true tangent line is important to make them look nice, that tool will sure help until you develop an eye for it. For an under the car header I would start with the front tube, tuck it in towards the block to make room for the others and then back out to where the collector is, top inside position at the collector. Start with the harder of the two sides too. Then you may be able to somewhat copy it on the other side or at least the basic look. Take the time to make a fixture to hold the collectors where you want them, it gives you something to shoot for. Anything will work, I've screwed the collector flange to a 2x4 and the 2x4 to a plywood base. Whatever it takes.
This is how things generally look for me during construction. Before they look like this Then I take them apart and weld all the tubes before welding them to the flange or collector. Makes life easier and you can check each tube for leaks. It's also a good time so send them out for extrude honing to clean up the inside of the welds. You'll probably skip that part first time around.
Thank-you. It's going in a channeled car with 3/4" cut off the bottom of the oil pan to get 5" of ground clearance and less than an inch of clearance from the air cleaners to the hood line. They had to tuck in to give enough clearance for the steering box and shaft and the fuel line on the other side. I would start with the tube that has the most critical clearance problems.
Pist-n-Broke, Absolutely, ^^^ Gas welding w/small torch, correct tip, and you're on your way. Just Mig or stick weld the Inside of tube to header flange, where it meets the head. Then grind flush.
The 2 most common mistakes first time around. Not having clear access to the plugs and space for Plug wires. And not being able to remove the Starter without dropping the header.