Here’s our new mill, just off the truck. This GM LS-series Gen IV V-8 is an aluminum block (with cast-iron cylinder liners) LH9 5.3L that produces 300 hp at 5,200 rpm and 320 lb-ft of torque at 3,600 rpm. The engine has variable valve timing (VVT) and active fuel management (AFM). The AFM cuts cylinders when the mill is loafing for better fuel economy. The horsepower and torque numbers will be better in the YJ than they are here, as we’ll be using a less restrictive exhaust than the OE trucks do. The LH9 has electronic throttle control, an extended-life accessory drivebelt, extended-life iridium spark plugs, and GM’s excellent oil life monitor system.
