6.5 Diesel

Bostic Motors Inc. 

We are Bostic Motors Inc. Not just on the internet, a real company with a real address and people that know about the 6.5 Diesel.

Chevy 6.5 DieselSince the 1990's, we have been building and servicing the 6.2L and the 6.5L diesel engine exclusively....including the new Optimizer 6500 ™

 Our operation has grown substantially in recent years, thanks in large part to our exposure on the modern Internet, and by offering the hard to find combination of high quality engines and parts at value prices. We have shipped our engines to every one of the 50 states and many worldwide including Canada, Australia, Norway, Germany and Sweden.

With diesel fuel costs rising and new diesel trucks costing $50-60K!, the GM 6.5 diesel engine has enjoyed resurgent interest among truck owners who realize that the 6.5 can offer unmatched fuel economy (often in the 18-21 mpg range). This easily bests the newer diesels such as GM's Duramax and the Ford 7.3 6.0 & 6.4 Liter engines. That fact, coupled with the improvements to the new 6.5 engines can mean great fuel economy and drastically enhanced durability / reliability.

We proudly supply engines and parts to the U.S. military, including Optimizer 6500 engines and service parts for the Civilian and US Military AM General built HMMWV. Recently we have been re-powering many retired military H-1's for customers who have been lucky enough to purchase these awsome machines at auction.

We don't offer or use "knock-off" or inferior Asian sourced parts, we specialize in New aftermarket and remanufactured Optmizer engines and components that can't be found at your local parts store.  If we sell something, its because we think it is the best offering of it's kind, at a below market price. No do-dads, no bolt on chrome, no promises that can't be fulfilled, just solid hardware for working trucks. That being said, much of what we can offer is not on the website, it would just serve to jumble the product offerings with lots of parts that may not be of interest to most people. Engines are the heart of what we do, so that is what dominates our site.

We employ experienced, and seasoned machinists and technicians, who machine the castings, then assemble our engines using all new O.E.M (mostly American, and NO Asian) parts to ensure a dependable, high quality product.

The design improvements and re-engineering of the new aftermarket castings add durability and virtually eliminate the potential for cracking in both the block and heads.

                 Our Improved Aftermarket & Optmizer 6.5 Engine  

Chevy 6.5 Turbo DieselFinally! ... 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). Bostic Motors 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.


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!


This new engine gains improved durability & longevity with a High Volume / High Pressure oiling system.


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.

Our Guarantee

Be assured with our Unlimited mileage, one year warranty covering every engine we sell. This includes both our New/Improved 6.5 & Our rebuilt 6.5 Diesel engine.

This also applies to engines used in commercial service.

You expect hard work from your diesel powered truck, and we'll guarantee it.

Assembly & Internal Components

 6.5 Liter Turbo Diesel Following assembly each engine is individually hot-run on the dynamometer. During this time the camshaft / lifters are properly run-in and the engine is monitored for any sign of oil or coolant leaks. All new and remanufactured engines are CNC machined, including line boring & decking. 

All engines are subjected to live dyno testing. This is why we don't generally offer short-block engines. Short-blocks can not be adequately tested on the dyno.

We are proud of our lengthy track record with the GM 6.5 Liter Turbo Diesel engine. We do not take risky shortcuts during the manufacturing / remanufacturing process. The grievous examples below are actually common practice with some "cut-rate" rebuilders.

  • We DO NOT weld on cracked cranks, blocks, caps or heads - or any part of our engines. If the parts are cracked, they are thrown away.
  • We DO NOT "sleeve" cracked blocks.
  • We DO NOT Cut or Machine any bearing surfaces on the 6.5 crankshaft - GM says this crank should never be cut!  (Nitrite coating)
  • We DO NOT use any Chinese castings or any cheap "White Box" internal engine parts from any Asian country!

 Compare to others: Our long blocks come with already installed; valve covers, oil pan, oil pickup tube, timing chain cover, new harmonic balancer.

All long blocks have NEW pistons, connecting rods, valves, valve springs, valve keepers, push rods, rocker arms, lifters, camshaft, timing chain, timing gears, valve guides, three angle seats, cam, rod and main bearings, piston rings, gaskets.

All our engines are upgraded to a High Volume / High Pressure oil pump.

The 6.5 TD desperately needs a boost of oil to the main bearings, this pump does the job like no other in the business!

All moving parts are NEW, with the only exception being the crankshaft. The crankshafts are magna fluxed and all bearing surfaces are restored. The service life of the crankshaft is effectively restored to like NEW condition after our polishing process is complete. Often the results are better than new, considering the personal attention each crankshaft gets in our facility as compared to the mass-output standards at the GM factory. A large percentage (60-80%) of the cranks that come back with the cores are unacceptable for use, therefore we actually replace a large percentage of cranks with new, however polished cranks and new cranks perform to the same standard.

Note: We do not cut/machine the crank or rod bearing surfaces, only a polish is acceptable by GM standards. If the crankshaft can not be properly restored with a polish, the crank is discarded.

We use MAHLE Clevite branded internal parts on both our new and remanufactured offerings. These are top quality O.E.M. parts from the same well-known industry leader that GM & AM General both continue to buy from.

Placing Your Order

6.5 Turbo Diesel EngineCall us at 828-453-7779 and speak to our knowledgeable sales department. Place your order or just ask a question. We accept Visa and Master Card or can securely process a check by phone.

We have replacement engines for any 6.5 L diesel / deisel engine application, turbo or non turbo, van or pickup, GMC, Chevy or Hummer / AM General

Please state year make, model and 8th character of VIN code when buying to be sure you receive the correct engine.

New glow plugs (if shown in the pictures) are not included with the long blocks,  but are included with drop-in's.

Installation of new glow plugs are required upon install for warranty to be in force.

Glow plugs are available with your engine order and can be shipped for no additional shipping charge.


Core Deposit

Gm 6.5 Diesel6.5 Turbo DieselThere is a $500.00 core deposit that will be refunded when rebuildable core is received back. Any of your core's deficiencies can be pro-rated and may not necessarily mean complete forfeiture of core deposit.

Just let us know when the core is ready, and our freight company will pickup the core. We pay return shipping for core.

Our domestic core deposit is just $500 for longblocks and $1500 for drop-in engines. International orders and export engines are $1000 for longblocks and $1500 for drop-in engines.

The core charge will be $1000-$1500 for international orders, since no core return is feasible due to shipping costs.


6.5 Turbo DieselShipping is by truck freight and cost is between $260-$450 depending on your location.

($260-$320 In East coast Region , $450 for parts of California, points between vary accordingly)

We can also quote for International shipping Rates.

Please Note: We request that you don't call or e-mail with retrofit of gas to diesel conversion questions. Conversions are generally not worth the effort or cost and entail quite a bit more then someone with limited experience may think.

Want the Best 6.5? | Our Guarantee | Internal Components | Placing Your Order | Core Deposit | Shipping


 Bostic Motors Inc. 157 North Main Street Bostic, NC 28018

   Ph# 828-453-7779 Fax 828-382-0298



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