I started fabricating the cold air box. The top frame is made of 1/8” flat and right-angle aluminum and it’s bolted through the 2” x 2” chassis tube with three 1/4” screws. It’s designed to: (1) allow the body to be removed with it in place which is important during the build and go-kart phase and (2) allow the air box to be removed with the body in place which is important once the car is finished (the wheel and wheel well liner must be removed first).
Underside of frame with Dzus springs installed
My plan is to fabricate aluminum closeout panels to dress up the engine compartment. With that in mind the lid for the cold air box is larger than it needed to be to cover the 2” x 2” chassis rail and to close the gap between cold air box and the wheel well liner. I used four Dzus fasteners to fasten the top to the frame.
Here’s how I got everything to line up perfectly. The placement of springs under the frame was tight so I flipped the frame upside down on the bench, located the springs and drilled a 1/8” hole at the center point of each spring. I then installed the frame on the chassis and clamped the lid in three places. Using the hole in the frame as a guide, I drilled upwards through the lid with a 1/8” bit and inserted a cleco to further clamp the lid to the frame. I repeated this for the remaining three holes. Now that the center hole for the Dzus connector was located, the left and right holes for the rivets needed to be drilled. To accomplish this, I fabricated a simple drill jig — three 1/8” holes, 1/2” apart in a straight line on a piece of scrap. I affixed the center hole of the jig to each hole in the frame with a cleco. After rotating the jig to the desired orientation (i.e. what would fit) I drilled the left hole with an 1/8” bit, inserted a cleco into that hole and drilled the right hole with the same bit. At this point, I had three perfectly spaced 1/8” holes, 1/2” apart in a straight line. The center hole was then enlarged with a 5/8” carbide hole cutter which had a 1/8” pilot so it was easy to get that part right. 1/8” flush rivets were used to affix the springs.
Left, center and right holes for Dzus connector
I repeated the process for the lid with four exceptions; (1) I used 4-40 screws rather than rivets because I didn’t want to drill clearance holes in the frame for the back of the rivets. The screws worked because the lid was 1/8” thick to prevent warping when welding, (2) the left and right holes were were drilled with a #43 bit and tapped, (3) the center hole was chamfered to get the Dzus connector to sit flat and (4) since there were no clearance issues the orientation was determined by what looked best rather than what would fit.
So that’s a total of 36 drilling operations. Screws or nutserts would have been a lot easier, but the convenience of the quarter-turn fasteners was worth the effort.
A bellmouth-style velocity stack was welded to the underside of the lid to reduce air turbulence. It also significantly stiffened the lid which kept it from warping when the 90-degree elbow was welded to the topside. The filter mounts directly to the velocity stack with a stainless steel clamp.
Velocity stack welded, upper elbow not welded yet and Dzus fasteners not installed yet
With the lid fastened via the Dzus connectors, a tight 90-degree elbow was positioned and tacked into place. The seam between the velocity stack and the elbow was welded on the inside and it was carefully ported. I defy you to find the seam in the picture below;-)
Velocity stack and elbow are ported; note that the screws for the Dzus connectors are flush
While not necessary, I had Abe weld the seam between the elbow and top because I didn’t want dirt getting stuck in seam. The picture below shows the finished lid with the Dezus fasteners tightened.
I’m not going to fabricate the actual box or the duct the connects the body to the air box at this point because I don’t need it for the first engine start. With both the source (filter) and the destination (throttle body) in place, it’s time to fabricate the induction tube and connect the two.