The pictures of this engine - from a super comp car - do a good job of showing headers made from SOLID CORE solder.
Here's how I made them.........
FIRST, find the right diameter solder for the size headers you are making ( .062 solder works for most cars, .093 works well for big-block and/or race cars). Don't ask me what size I used, because I always build "by what looks right"!
Then drill the same sized holes ( 4 on each side ) into the engine block where the headers will mount.
Then, BEFORE painting the block, attach some photoetched Detail Master header flanges that have the same diameter hole as the ones drilled to mount the 4 header "tubes" ( or as close as possible ).
Paint the block in your choice of colors and let it dry completely.
After dry, sand the paint off of the photoetched flanges. This will give you an aluminum look, plus it will slightly round the edges of the flanges.
Cut a length of solder for a header "tube". Roll the length of solder between a couple pieces of glass to smooth out the solder.
If you want to polish the header "tube", now is the time!
Fit the solder through the photoetched flange and into the hole in either the front or rear-most header location - it doesn't really matter - and into the block about 1/2" ......this will give you room to shift the "tube" in or out of the block as needed.
Repeat this for the rest of the "tubes on one side of the block.
Make any bends needed in the individual "tubes" and bring the 4 of them together at the point where the header collector will attach and fasten them using 5 minute epoxy and wrapped with a strip of tape until the epoxy sets up.
When ready, trim the 4 "tubes" evenly, leaving them a little long. I then bevel the edge of each tube until the 4 of them form a point.
Make a "collector" from aluminum tubing, using tubing that has an inside diameter that will fit over the ends of all 4 "tubes". I then thin the inside of the aluminum tubing using an xacto knife, so that when the "collector" is placed over the ends of the "tubes", I can use the tip of a small flat-tip screwdriver to fit the tubing snugly around each of the header "tubes".
Attach the "collector" with epoxy, then, when both sides are done, attach then to the block!
I hope I haven't been too confusing! Once you get started on making them, you'll get more of an idea as to what I'm rambling on about.