Our new 6.5L project will begin with this GEP Optimizer 6500 long-block. Basically, this engine is the latest version of the 6.5L V-8 diesel you've been able to buy in GM trucks since 1982. Our version is a hybrid of sorts, built by Dennis Sweeney of General Engine Powered Products, and uses the mechanical injection and thermostat housing off an early 6.2L and the turbocharger and intake off the latest 6.5L. |
In order to unlock the potential of our 6.5L, Sweeney built our engine with larger valves from the naturally aspirated 6.2L and a Holset turbocharger. The turbo is tied to a side-mount exhaust manifold from the late-model pickup truck and will be fueled by a Stanadyne DB4 mechanical injection pump and injectors from a marine application 6.5L. |
Common 6.2/6.5L Problems
The 6.2 and 6.5L engines weren't without fault. Over the years, the GM design has been plagued with start-up and overheating issues more than true durability problems. Many of the troubles you read about online can be traced back to the emissions-control systems: glow-plug controller, injection-pump controller, or EGR. Remember, these engines were certified by GM for use in 11/42-, 31/44-, and 1-ton trucks (even in California), so there was a lot of emissions equipment found on these engines that didn't make it onto the Cummins and Power Strokes until just recently. That also means that 6.2 and 6.5Ls in 1-ton trucks and Hummers are likely to be more reliable because they have less emissions hardware.
However, there are a few areas that we'd keep an eye out for with any 6.2 or 6.5L. Because these engines use an indirect-injection they need larger cooling systems than other gasoline or diesel engines. Cooling wasn't a huge problem in the early 6.2L days, but as the power ratings increased and the new '88-'98 body style came to market, overheating seemed to become more common.
Here's what we'd watch out for:
*Coolant leaks: Caused by external hoses and head-gasket failure, especially on '88-'96 trucks.
*Oil leaks: Oil pan design and early rear main seal are likely problems.
*Hard starting: Glow plugs prone to failure due to malfunctioning glow-plug controller. High compression ratios and the starter solenoid design only added to the problem.
*Excessive engine vibration: Due to harmonic balancer separating, which leads to crankshaft failure.
*Cylinder-head cracking: Due to overheating or poor casting quality.
*Engine-block failure: Due to insufficient casting quality, '00-and-later blocks are best.
*Electronic-injection-pump failure: Caused by overheated pump-mounted driver (PMD) and not a failed injection pump.
The New AM General Optimizer 6.5L
General Motors no longer builds the 6.5L diesel. General Engine Products (GEP), a division of AM General (yup, those guys that build the Hummer), produces what it calls the Optimizer 6500 engine in its Franklin, Ohio, assembly plant; General Engine Product's engine facility went into operation in July 2000. Before that, the 6.5L was built by General Motors at its Moraine Engine Plant. With GM's technical support, GEP developed the new facility and made numerous improvements to the engine. Today, the Optimizer 6500 engine is found in new military HMMWVs, H1s, and as a service replacement engine for GM 6.2 and 6.5Ls.