The problem was simple: the engine had more in it, but the stock intake manifold was holding it back. Once we saw the airflow limitation, the answer was to get rid of the factory-style layout, open up the intake side, and build a side-draft manifold that let the ports do their job. That change was a big part of taking a used Cummins dyno engine from roughly 400 horsepower to 735 horsepower at about 3,100 rpm, then backing it up in a streetable truck that set a 217 mph two-way average at Bonneville. That same thinking is why Big Hoss is coming back for the Ram 6.7L. Better airflow is the real win. When the manifold stops being the restriction, the engine can breathe cleaner and make honest performance improvements.
Gale begins by pointing to a 24-valve Cummins side-draft manifold and reflecting on how the idea started roughly 24 years earlier, around 2001. At that time he met John Stang, who was running what he describes as the Cummins skunk works. Cummins stock was depressed, at about $27 per share, and Gale believed the company needed both a technical boost and a way to attract younger investors. His view was that Cummins could become more culturally relevant if it paired its diesel engineering with a high-profile performance project.
Cummins was preparing a common-rail version of the 5.9-liter engine for the 2003 model year, and Gale saw that injection technology as the right foundation for a record-setting truck. He considered the common-rail system a major advantage and proposed using it in a pickup application. His goal was not simply to build a race-only vehicle. He wanted enough power to chase speed records while keeping the truck streetable and practical enough to tow the team's pit trailer, including tools, a workbench, wheels and tires, and quick-change gears.
Cummins agreed to support the effort only in a limited way. There was no development budget, but they did provide a couple of used dyno engines. Those engines had reportedly made about 404 horsepower. When Gale's team tested one on their own dyno, it produced about 402 horsepower, close enough to confirm that both sides were working from the same baseline. That agreement mattered because it established credibility before any serious engineering changes began.
From that 400-horsepower starting point, the team concluded that the engine's main restriction was airflow. If they wanted to move substantially beyond the stock output, they would have to address how air entered the engine. The factory intake manifold quickly became the primary target. Gale recalls looking at it and deciding that it had to go, especially because they also wanted access to port the intake passages in the cylinder head. Once they began evaluating the bolt pattern and packaging constraints, the project evolved into a more comprehensive redesign of the induction side of the engine.
The solution was to modify the head and design a casting for what Gale calls the Big Hoss side-draft intake manifold. On the exhaust side, the team built a fabricated manifold to complement the new intake arrangement. These changes were not cosmetic; they were part of a deliberate airflow strategy intended to support much higher power at usable engine speed. After completing the induction, head, and exhaust work, the engine reached 735 horsepower at about 3,100 RPM. That represented a dramatic increase from the roughly 400-horsepower baseline and validated the team's conclusion that airflow was the central obstacle.
When Gale called Cummins engineering to report the new output, the initial reaction was disbelief. He recalls being told, in effect, that the number sounded impossible. That response underscores how large the gain was relative to the starting point and how unconventional the path had been. The side-draft manifold and associated airflow work had transformed the engine far beyond what the original used dyno engines suggested.
The finished engine was installed in a truck with an automatic transmission, and the team drove it to Bonneville. In keeping with Gale's original intent, the truck was not treated as a fragile, single-purpose race machine during transport. Once on the salt, they converted it into race trim and proceeded to make record attempts. Gale emphasizes how normal the truck still felt in that setting, recalling that he drove it to the starting line with a country radio station playing.
The truck broke the record on its first run, but Bonneville records require a two-way average rather than a single pass. The team's best two-way average was 217 mph, while the best one-way speed, measured at the back door out of the fifth mile, was 222 mph. Those numbers confirmed that the combination of common-rail 5.9 power, major airflow improvements, and practical truck packaging had achieved exactly what Gale set out to do: build a streetable diesel pickup capable of record-setting speed.
Gale identifies the manifold on display as the world's first side-draft Cummins manifold for a B-series 5.9 Cummins and says it belongs to the record engine. He has now decided to bring back the Big Hoss concept, this time specifically designed as a cast manifold to fit the 6.7. He also says he wants the new version to be affordable. He closes by noting that Cummins did not pay for the truck's development. The company did not participate in the build cost, and he pursued the project because of his own enthusiasm for diesel performance, something he says has never gone away.
