Fabrication of the 180 cross-under headers has begun. The first step when routing anything, especially hard tubing, is to establish the start and end targets. Setting up the starting points was easy. I simply bolted cast stainless steel exhaust flanges from Ultimate Headers to the heads. The merge collectors are the end targets. Since mine are located as low as possible I clamped a piece of 3/4” plywood to the bottom of chassis, 3D-printed spacers and clamped the backsides of the merge collectors to the plywood.
3/4” plywood clamped to underside of chassis and rear of merge collector affixed via 3D-printed spacer and clamp
The fronts of the merge collectors were held in place by 8-32 screws passing through the gap between the primaries — I didn’t have any that were long enough so Abe welded two 3” long screws end to end.
Note how far the bellhousing flange extends below the Daily dry-sump oil pan. This is what provides the space for the primaries to cross under the engine.
Upper half of left side. Several of tubes have been tacked, the horizontal one is clamped
This picture illustrates why it was necessary to scallop the chassis tubes. A tack-welding clamp in middle of outer primary.
The icengineworks tack-welding clamps are very useful. They allow the orientation of the tubes to be clocked while ensuring that they are concentric. When everything is where you want it you tighten the nuts and nothing will move. They have large openings that allow the tubes to be tacked. I have two sets of clamps, 1-7/8” and 2”, to support the stepped primaries. We were not able to get either to work at the transition joints so we took one of each apart and created two clamps with a different diameter on each side. It worked well.
Removing all of the marks made by the bending dies is a lot of work. I used the tube polisher discussed in an earlier post, starting with 120-grit sandpaper and finishing with a Scotch-Brite surface conditioning belt. The trickiest parts are the outside radiuses because any lateral pressure causes the belt to pop off of the tracks and fall on the floor.
There is a lot more fabrication required to finish these up.