Mil-Spec Automotive set out to do for Hummer H1s what Singer does for Porsche 911s, rebuilding them to a Swiss-watch standard, modernizing them with myriad upgrades, and then pricing them like Fabergé eggs. We pointed out some chips in the enamel of MSA’s original egg when we drove a Mil-Spec Hummer H1 in 2018, but the company has spent the pandemic developing a second generation of its H1 build, which it dubs the M1 or M1-R, depending on its state of tune. The upgrades make it even more worthy of consideration, with factory-original used examples of the low-production 2006 Hummer H1 Alpha fetching $200,000 or more at auction.
As before, the most crucial MSA upgrade is to the Hummer’s wheezing stock diesel or small block gasoline powertrain. Those pitiful V-8s are replaced by a 2006-2007.5 model-year 6.6-liter Duramax diesel. The Mil-Spec team regards this LBZ engine as “the last of the hot-rod diesels.” As before, HSP Diesel Performance & Accessories of Romeo, Michigan does an extensive balance and blueprint rebuild, strengthening various components to withstand power and torque that gets elevated from the stock 350-hp/650-lb-ft rating to 500 hp and 1,000 lb-ft in M1 spec (that’s about what the first-gen MSA H1s produced). This engine runs EGR to preserve the emissions compliance required of the 1992-2004 model-year VINs appearing on these civilian Hummers’ titles (this one’s a 1998). Spending $60,000 on the Intrepid Performance Package turns the wick up to 800 hp and 1,300 lb-ft.
Achieving either output requires a much larger turbo and intercooler, an upgraded Bosch fuel-injection system, and a new engine controller, and managing that enhanced output requires an equally robust transmission. In this case, that’s an Allison 1000 T6 six-speed automatic, also reinforced by HSP to either Stage 3 or Stage 5 standards, depending on engine output. A new electronic gear selector and transmission controller provides access to all six gears via optional steering-wheel paddles or console buttons (the stock mechanical shifter only featured D-2-1 positions). For the full story, check out this article from Motor Trend.