Munster then scrapped the rear Dodge leaf springs, shortened the wheel base slightly and built his own truck arms and panhard bar. “I wanted to have air ride in the rear so the truck will ride nice when it’s empty and I can air it up when I have sleds on,” he explained. “I thought I might as well do the front air ride as well, so I bought a front air ride kit from Kelderman and additional bags for the rear.”
To finish it off, Munster had Filthy Motorsports build him a custom-valved set of King 2.5 Smoothie shocks. To run on board air, he converted the stock AC pump to a grease lubrication system so it could be used as a compressor pump. The air ride control is inside the cab. There are two gauges with four needles that read psi, and each corner can be adjusted by pneumatic switches.
Munster said the engine and 5-speed transmission were completely stripped down and rebuilt. The transmission was built with new synchros and bearings. “I made sure to shim the bearing lash a little bit on the tighter side of the recommended tolerance,” he explained. “The Cummins motor just seems to amplify any slop in the drive train and my goal was to make this truck as tight feeling as possible. Of course, the fifth gear nut was fixed with a splined nut retainer, and the fifth gear itself was replaced as well.”
Since the output shaft splines were in good shape, Munster said he didn’t bother to upgrade the shaft. However, he bought a South Bend clutch kit that came with a new flywheel since he wanted to get a clutch that could handle the extra horse power, but still have a light foot pedal disengagement.
Next, the engine block was sent out for machining where it was magnafluxed, honed and decked. The valve seats in the head were machined and stiffer exhaust valve springs were installed to accommodate a different exhaust brake.
Munster then rebuilt the bottom end with all new bearings and installed new Mahl pistons.
“I also installed a high flow oil pump that comes on the 24-valve to get a little more oil pressure,” he said. “The head was bolted down with ARP head studs and a .010-inch oversized Victor head gasket was used to make the clearance I needed after decking the block.”
The injection pump was sent out to NW Fuel Injection where it was fully rebuilt and retimed. The timing was set to 15 degree total advance and the governor was set to 3,000 rpm. The stock 215 injectors were also flow tested to make sure they were in good shape. The pump was tuned to move 320cc of fuel at full boost, which is a mild 400 horsepower or so.
“My plan was to make a very reliable and drivable 400 horsepower with low EGTs,” he said. “Now that I had the basics covered, I installed a BD Stainless Exhaust manifold and an AST Aurora 3000 Turbo.”
Munster said he did a lot of research on what turbo to choose, and went with the Aurora 3000 mainly because it fit into a good efficiency range with the horsepower he was going to be making, and still had a fast spool-up.
“Another benefit to the Aurora 3000 is it doesn’t have a waste gate, which made it the perfect partner with the supercharger I planned to bolt on before it,” he explained. To make the truck really shine in the drivability category, Munster managed to make room for a Procharger D-1SC by moving the alternator on top of the engine and putting the Procharger in its place.
“A centrifugal supercharger has an exponential boost curve which made it a good candidate to keep up with the turbo,” he said. “I have seen some positive displacement chargers used on diesel engines in the past, and in most cases it seems to be a restriction once the turbo starts building boost and moving a lot of air.”
Munster said his main concern with the Procharger was getting it to spin fast enough to keep up with the turbo, especially when the Cummins engine spins at such a low RPM and the Procharger is only driven off the main 8-rib serpentine belt.
“This was all a big experiment to say the least,” Munster said. “Nobody seems to make pulleys for the Procharger small enough for my application, so I started making my own on the lathe.”
After making three different sizes, Munster finally got some good results. “Surprisingly, even at the largest pulley size I tried, the supercharger would supply positive pressure to the turbo all the way through the rpm curve regardless of how much boost the turbo was producing,” he said. “Almost like the centrifugal force of the Procharger would make a set pressure to the turbo based on rpm alone.”
The engine load, CFM and turbo boost pressure seemed to make very little difference to the boost the supercharger was supplying to the turbo. After making a small enough pulley to reach the boost numbers Munster wanted, the truck started to drive more like a supercharged car than a laggy turbo diesel.
“This is easily my favorite mod to the truck by far,” he explained. “Under full load the supercharger will reach numbers of about 10 psi supplied to the turbo, and the total boost pressure of the turbo will hit just over 50 psi, with EGTs just barely scratching 1100 degrees.”