Around the inlets the welded flange is cut off to give clearance for the exhaust stud nuts. The flange is also cut off at the outlet end for the elbow to slip over.
I thought about all sort of complicated tools to mark the cut lines. In the end I decided to use the old form block, which was setting around. I drew the cut lines for the ends of the cut offs on the block. Then I placed a shell in the block and drew the lines on the shell, using the lines on the block as a guide.
To make the cuts easy I punched 1/4" holes in the corners using the line as a guide. Normally I would center punch where I want the hole. In this case the hole location is not that critical. Instead I turned the Whitney Punch upside down and looked through the hole in the die to line up the edge of the hole with the line. You have to clear out the slug in the die after each punch so you can see the line, but it worked fine
I realized part way through that a red line was easier to see in the die hole than the pencil line I started with.
For the outlet end I needed to first cut off the excess metal from the forming operation. I had started making a tool for shaping this end during assembly, more on it later. I decided it would make a good guide for drawing the cut line because it would stay square in the shell. Just position it in the shell and draw a pencil line along it.
I cut the end off with the band saw.
I could have used a supports for the shell while sawing. I was able to tip the shell for half the cut and support the flange with a block of wood for the other half of the cut.
To clean up the cut I just used the belt sander and deburred the edge.
Once the outlet end was cut off I just used the snips to cut along the lines I drew and to follow the edge of the tube to the hole. You need left and right snips to do this.
They came out very good. They're starting to look like parts which could make the manifolds.
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