D&J Precision Machine Moves Past Cummins With Two LML Duramax Long Blocks

D&J Precision Machine built its name on Cummins engines. Now the Ohio shop is selling its first Duramax: remanufactured long blocks for the 6.6-liter LML in 2011 to 2016 Chevrolet Silverado and GMC Sierra 2500HD and 3500HD trucks. Diesel Army reported the launch on October 1.

“LML owners depend on these trucks for work, towing and everyday driving,” said D&J CEO Drew Pumphrey, as quoted by Diesel Army. This is not a big-power competition engine. It is a carefully rebuilt stock-displacement engine for the people who need their truck back.

Essentials vs. Precision Plus

Both engines start with a full teardown. The block is CNC blueprinted, bored, honed and deck-surfaced, the crank is checked and repaired as needed, and new OEM-spec Tier 1 pistons and rings go in. The crank and cam are keyed to prevent gear movement, and the heads are resurfaced with recut seats, new valves and L5P-style top-hat valve stem seals. New lifters, valve springs and freeze plugs are standard.

The Essentials uses Tier 1 head gaskets and reuses applicable parts from your old engine. The Precision Plus adds multi-layer-steel head gaskets with ARP head studs, an L5P oil cooler, a pinned oil pump drive, and ships much more complete, with rocker assemblies, pushrods, valve covers, intake manifold, harmonic balancer, flywheel and flex plate.

Why it matters

The LML is now a ten-year-old engine, and a lot of these trucks are on their second or third owner with serious miles. Every engine is tested in-house on RMC ETS equipment for compression and cooling-system integrity before it ships, and the warranty covers 24 months or 100,000 miles on parts and 24 months on labor, subject to D&J's terms. For HD owners who want a known rebuild instead of a junkyard gamble, that is the pitch. D&J also lists complementary parts for the same trucks, including LML turbos, remanufactured injectors and a CP3 conversion kit, so a full refresh can come from one place. For a work truck that has to be back on the road towing, a single warranty covering the whole long block is worth real money.