Fitting Exhaust Manifold Shells To Fixture

In theory the formed shells should fit right onto the assembly fixture.  They would except I made a mistake when I made the form block.  For reasons I'll never know I made the inlet openings in the form block 1 3/4" wide when the exhaust opening in the cylinder is 1 7/8" wide.

To fix this I carefully shaved 1/16" from each side of each inlet opening in the form block.  I then went back to the hardware store and found a 1 1/8" bolt, the flats are 1 13/16" across, and cut it like I did the 1" bolt I used originally.  Then I clamped each shell back in the form block, with all 32 bolts, and re-formed the inlet with the new bolt/form tool.  It was slow but it worked.

 I also added a cut off reference line on the form block so I could mark where to cut off the excess steel.  I still left a little excess which I will trim once the flange is welded on.



The shell now fits snugly in the flange I borrowed from John Gaertner.

 To trim the excess I first cut the sides with tin snips.  I used a left and a right snip so the excess would deform not the shell.

Then the flat was cut with the band saw.

The last step was to clean up the cut end with the belt sander and deburr it with a file.

 Now the shells fit the fixture perfectly.  Actually the 3/8" segments for the blocks worked out perfect.  I left 3/8" past the center line for the exhaust flange so I just line up the ends with the joint between the first and second blocks in the stack.

I hold each inlet tight to the it's block while clamping it on the sides to flatten and square up the sides.  Then I hammer the top to flatten it to the block.  When all 4 are done on to the next shell.

Next I need to trim the sides of each inlet to the finished length for welding.