This manifold is doing more than feeding air into a supercharged Duramax. It has to seal cleanly, carry blower and belt loads, package around the charge air cooler, and make nitrous distribution as even as possible. That is why we looked hard at the sealing surface, nozzle geometry, and structure instead of just adding ports and calling it done. For sealing, the goal is controlled RTV with a proper squeeze gap so excess material stays contained instead of squeezing into the intake path. For nitrous, the better move is to use the plenum volume to help mix the charge rather than shooting straight down at individual runners. That gives us a better shot at uniform cylinder distribution. And because the blower drive puts a real bending load into the inlet area, the upper manifold gets ribbing for stiffness and a support tied into the front drive structure. The result is a manifold designed as a system: airflow, sealing, nitrous placement, structure, and packaging all working together.
The episode centers on a tight fabrication deadline for the supercharged Duramax. A newly printed intake component is already on its way to Shawn at Empire Fab, but he still needs the intake tubes before he can finalize the hood cut. Because recent dimensional changes altered the tube geometry, Eric has to remake the tubes quickly and accurately enough that Shawn can continue bodywork without waiting on the truck itself.
Since the vehicle is not available for direct fitment, Eric builds a substitute fixture from CAD data. Matt sends over an isolated model of the intake tube, and Eric uses it to create a simple tab-and-slot steel jig in CAD. The two intake tubes will be mirrored parts, but both can be built from the same fixture. He plans to cut the jig on the Torchmate so it keys together easily and can be welded into a rigid stand-in for the truck-side geometry.
The mandrel bends create an additional challenge. These bends have an unusually tight radius and provide essentially no straight section for clamping or referencing. Normally, a mandrel bend includes some straight length that makes setup much easier, but that is not the case here. To compensate, Eric designs 3D-printed soft jaws that cradle the tubing at the exact orientation needed for cutting. He pockets the printed fixture primarily to reduce print time, since speed matters more than durability for this one-off operation. The printed jaws let him slide the bend into position, lock in the angle, and trust the cut location well enough to proceed without repeated trial fitting.
With the fixture complete, Eric moves to cutting the stainless tubing. He doubles up on clamps and works the mandrel-bent section through the soft jaws without disturbing the setup between cuts. To verify squareness, he marks the bottom tangent of the tube with a red Sharpie before cutting so he can inspect how true the saw cut is afterward. The result is better than expected, especially considering the age of the saw.
For the larger angled cut, he uses the first saw path as his zero reference. The target angle is 76.3 degrees. Measuring from the backside edge against the table gives him 80.3 degrees, but because the saw uses a tilt table, he also has to account for a 0.5-degree blade tilt already built into the setup. In practical terms, he needs to remove 4 degrees from the 80.3-degree condition to reach 76.3, but the existing 0.5-degree tilt means the saw only needs an additional 3.5 degrees of adjustment. He zeros his angle gauge from the first cut, sets the saw to 3.5 degrees, locks it down, and runs the cut with the expectation that it will land as close as possible to the required 76.3 degrees.
Thin-wall stainless tubing tends to grab the bandsaw blade and spin, but simply clamping harder can deform the tube. Eric avoids that by inserting a machined Delrin slug into the tube. The Delrin piece is slightly smaller than the tube's inside diameter, so it supports the wall internally while allowing the clamps to be tightened much more aggressively. That prevents the tube from collapsing or twisting during the cut.
Once all the pieces are cut, Eric assembles them on the jig. The set includes the large bend, a smaller sliced section, and the straight pieces. The jig works well overall, though he has to add a chamfer to accommodate one HD clamp he initially overlooked. After checking fitment, he disassembles the parts, cleans them, and Scotch-Brites the surfaces. He only tack-welds the tubes at this stage because speed is critical and a second mirrored tube still has to be built. As soon as both assemblies are tacked, they are sent to Shawn so he can continue the hood work without delay.
The fabrication work at Empire Fab has also progressed on the cab. The metal has been cut, and the lower firewall section on the driver's side has already been formed. Openings are in place for the cross braces, master cylinders, and steering. The team also created space-claim mockups representing the future valve covers and transferred those outlines onto both sides of the firewall so the surrounding sheet metal can be shaped with the final engine package in mind.
A recessed kickback pocket has been added for the intercooler fittings, and that recess is visible from inside the cab as part of the firewall structure. The main transmission tunnel is currently made as two pieces, but it will be welded and metal-finished into a single continuous section. Additional shrinking work has been done at the rear to pull the tunnel down around the back of the Allison transmission. The driveline tunnel has also been enlarged slightly beyond the original request to provide extra clearance for what may become a larger driveshaft. That tunnel was stepped up in size and raised somewhat to ensure adequate room.
The next steps are to weld in the current cab panels and fabricate the remaining closeout pieces. Front engine-bay tubs are still waiting on the return of the core support. Those tubs and the firewall will be designed together, since the final firewall layout depends on how the tubs resolve once the core support is back in place.
Attention then shifts to the intake manifold and nitrous integration. The manifold design is far enough along that the team reviews mounting, sealing, service access, and nozzle placement. The upper manifold includes wrenching cavities for fastener access, while some lower bolts remain accessible from the outside. The flange thickness is called out at 0.340 inch, or 8.636 millimeters.
The manifold is designed to drop onto the engine using dowel alignment. The factory arrangement uses two separate manifolds, each independently doweled, but this one-piece design cannot be doweled on both sides without making installation impossible. Instead, the team dowels one side, using dowels at two locations to establish rotational control and visible alignment, then bolts the manifold down from there. That gives enough positional accuracy while still allowing the part to be installed on the engine.
The initial sealing plan follows the factory method and uses RTV between the intake manifold and cylinder head, but Gale questions whether an O-ring could be used instead. The discussion turns to squeeze-gap design, a method the team also uses on cast aluminum oil pans. In that approach, RTV is machine-applied to the sealing surface, then compressed between the mating parts in a controlled geometry that leaves a defined squeeze gap.
The purpose of the squeeze gap is to prevent excess RTV from extruding inward and hanging into the airflow path, where pieces could eventually break off and be ingested by the engine. In the CAD cross-section, the squeeze gap is shown as a feature that captures the sealant while still leaving enough compressed material to do its job. After reviewing the geometry, the team agrees that a properly controlled squeeze-gap RTV seal is acceptable if the RTV can be deposited accurately. That becomes the preferred path rather than redesigning the manifold for an O-ring at that interface.
The manifold will incorporate an Elemental setup with two stages of nitrous, with the possibility of running only two nozzles initially and adding the other two later. The current concept uses four nitrous outlets with 45-degree tips that are slightly angled to clear the charge-air cooler and manifold geometry. Even so, Gale is concerned less with packaging than with distribution. Rather than aiming nitrous down toward individual runners, he wants to use the upper cavity of the manifold as a mixing plenum so the nitrous disperses more uniformly cylinder to cylinder.
That leads to a discussion about nozzle orientation, clocking, and plume behavior. The team considers shortening the nozzles and spraying laterally into the plenum instead of downward. Because the nozzles use pipe thread, clocking them precisely is difficult, which complicates any design that depends on exact rotational orientation. There is also concern that opposing lateral sprays could impinge on nearby surfaces or on each other, depending on the final plume shape. The conclusion is to keep moving forward with manifold manufacturing while continuing to refine nozzle length, angle, and outlet geometry with Mike Thermos, whom Gale identifies as the originator of Nitrous Oxide Systems and a key technical resource on the project.
The upper manifold will carry the nitrous bosses and threads, while the lower manifold will remain untouched. The nozzles will penetrate through the upper structure near the heat-exchanger flange area, and the team reviews cross-sections to confirm that the nozzle path clears nearby O-ring features. A thermocouple location is also visible in the model, which should provide useful data once the system is operating.
Beyond airflow and nitrous, the manifold receives structural refinement. Styling ribs added to the upper manifold are not merely cosmetic; they also stiffen a relatively thin-wall region that is about 0.200 inch thick. The inlet will be tied into a front-engine accessory structure, creating a support point that helps carry the load from the belt drive and tensioner. That matters because the supercharger belt requires substantial tension to grip the pulley, and that tension creates a significant bending moment on the manifold and blower mounting structure.
The team also reviews the rear heat-exchanger fittings. They want to route coolant connections through the back of the manifold while maximizing firewall clearance, so instead of using hard 90-degree turns they plan to make their own fittings that shift the outlets forward enough to allow softer, radiused 90s. Satab fittings were referenced in the CAD review, and the internal diameter under discussion is 15.5 millimeters, approximately 0.610 inch, which prompts a comparison to 5/8 inch. With the manifold geometry, support strategy, and fitting direction all looking favorable, the review ends with approval to proceed and ship the design. The next fabrication phase will move on to the articulating bed.