Our Improved Aftermarket & Optmizer 6.5 Engine

Finally! … you can have all of GM and AM General’s most recent 6.5 engine updates at a much more affordable price than the dealer can offer. These engines are assembled using All New redesigned block and heads to address the cracking issues that plagued the original 6.5 GM castings. The design improvements and re-engineering of the new castings add durability and virtually eliminate the potential for cracking for both the block and heads.
Here is What is New and Improved About These Engines:
These engines are built using the New & Improved Block and Head Castings.
Our improved engines also include improvements to the internal components and oiling systems.
Just a few of the many details that set our engine offerings apart from almost all others:
1). Our remanufactured Optimizer™ engines utilize genuine AM General 2004 and newer Optimizer military issued block and head castings. These updated castings have eliminated cracking and oiling issues.
2). We hot-run dyno test every engine before shipping, to be sure of catching coolant and oil leaks and being sure all internal parts are seated and operating as they should be at the correct oil pressures.
3). We are using OEM and OEM supplier (MAHLE Clevite) parts for all internals.
4). WE DO NOT use any Asian sourced parts or components.
5). We do not cut the crankshaft, nor do we use cut crankshafts, as cutting the 6.5 crankshaft is strictly not permitted by GM protocol and factory published technical service bulletins.
6). BMI cares about their customers and is very interested in helping (and assuring) the installer get the engine installed properly, buy utilizing historical data and making a point of highlighting specific problem areas that may be faced during an install of this unique and (formally) problematic engine.
7). We pay for the return of the core.
BLOCK & HEADS:
The iron used in the new block utilizes molybdenum, a metal yielding a 20-25% increase in strength, without being brittle. The new block design also incorporates improved main bearing webs and caps. In addition, the head bolt holes in the block deck are strengthened, vastly improving head gasket durability. Additionally, changes of the water jacket design in the heads have helped address the 6.5’s overheating problems. The original 6.5 & 6.2 cylinder heads produced by GM were prone to developing small cracks between the valves. The new redesigned heads have added chromium to the cast-iron to virtually eliminate these and other cracking issues.
Our new blocks are NOT from China. Blocks are received as raw castings from a large reputable foundry that continues to produce the OEM 6.5 castings. Then the CNC machining for bore and decking is completed. This process offers a far superior platform for the engine build-up than Asian sourced pre-machined aftermarket blocks. This new block and head system offers complete parts interchangeability & bolt hole alignment as your original block, because it is the original block, just better!
OILING SYSTEM:
This new engine gains improved durability & longevity with a High Volume / High Pressure oiling system.
INTERNAL COMPONENTS:
Mahle Clevite has significantly improved both the Pistons and Connecting Rods since the time that the 6.5 was used by General Motors. The Connecting rods are more durable and the Pistons are stronger and lighter.
With these important improvements, Our new 6.5 is among the toughest, longest lasting 6.5L diesel engines available today.
Not one block or head crack issue to date. – Now that’s what we mean by improvement.
Some other companies are claiming to sell new block/head engines, but be careful, many are new block/heads using the old casting forms, no improvements and poor quality alloys- FROM CHINA! . Booooo! There is only a handful of others offering the real IMPROVED & UPDATED castings aside from AM General and General Motors themselves. If it’s not OEM,…. What is it?
Available as a long block & as a ‘drop-in’ – Click on our products page button below, or at the top of this page for more details and pricing.

We also offer a 6.5 Marine Diesel engine. These engines are built specifically for Marine applications with an 18:1 ratio and forged crank.
We also build 6.2 L engines, including very limited supplies of N.O.S. new / improved 6.2 blocks.