Trim Line For Exhaust Shells

 I haven't finished the exhaust manifolds because I've been busy on other things and I didn't like any of my ideas for trimming the shells and for forming the edge overlap bends.

I've had a great idea for marking the trim line on the shells.  It's kind of the reverse of scribing a line on a board with a marking gauge.  Instead of the guide being on the scale, the guide is the rounded end of the block of wood.

For a scribe I used a coarse thread drywall screw.  I drilled a hole at the distance for the flange on the lower shell and a hole 1/4" further out for flange on the top shell.  The edge of the top shell wraps around the edge of the bottom shell to make a nice finished edge.  You adjust the screw tip, for the line you want, to just stick out of the block.  Run the block around the part leaving a nice even trim line.

Too simple.