The was not happy with how different the louvres were between the bonnet and intake even though they were from the same Landcruiser model. So I thought I would try to make some matching ones to replace them with. First took a pattern of the shape.
Transferred the shape of the louver to some 8 mm/ 5/16" flat I had. Used a hole-saw to get a start and then nibbled away at it with a jigsaw and then a file. This is a little thicker than the height of the louvers, but would allow for some spring back. The middle part was cut out just using a angle grinder. The thickness each side of the opening is set to the gap I wanted between each louvre.
Tig welded it onto more of the same flat to get a good base to it and stop the sides from spreading. Filled it with oil to cool as might add a little hardness to it without getting brittle like a water quench. Using a great tip from Per, MetalMan Sweden, I used a wood chisel sharpened with a curve to the end to cut the metal. https://www.youtube.com/watch?v=vIPZUUPPTFk Could also drill a small hole at each end and use a thin cutting disc, but leaves a bigger hole not covered by the louver.
Used a bit of very hard red gum to shape into a forming tool. It is important that it is the full width of the louver. I found starting in the corners and lots of small taps to just cut through the metal and no further worked best for me. I scribed lines to follow where to cut and made sure the metal didn't move on the form. You need to hit down right on the very edge for it to work.
I kept the form straight to get consistent shape. The corners need to be a bit ahead of the rest and use plenty of light taps with the mallet working back and forth like a reciprocating machine. 4 down and two still to go. Matches the shape of the template pretty well.