What is the Optimizer 6500 Engine?

• GM Introduced in 1992 as replacement for 6.2L diesel

• GM production ended in 1999

  • Rights were sold to General Engine Products

• Continued production by General Engine Products (GEP) in 2001

  • GEP is a Subsidiary of AM General Corporation. The manufacturer of the HMMWV and Hummer H1

  • The trademark name changed from "6.5L Turbo Diesel" to "Optimizer 6500"

  • Current production continues to this day

1. Fire Deck Issues

   • 1994-1998 turbocharged blocks prone to circumference cracking

   • Number 8 cylinder particularly vulnerable

   • Rear cylinder cooling problems

2. Main Bearing Concerns

   • Original design had insufficient bulkhead strength

   • Main cap and bolt issues in early models

3. Cylinder Head Cracking

   1. Every set of GM heads ever produced can and will crack at the valve seats

• Optimizer Block Updates:

  • Thicker bulkhead (+.020")

  • Taller main caps

  • Molybdenum-enhanced iron casting

  • 10mm outer main cap bolts (vs. original 12mm)

  • Modern CNC block preparation

  • Modern assembly line and Quality Control processes

1. Optimizer Head Improvements

   • Induction hardened valve seat area

   • Four cooling passages between valve seats

Crankshaft Specifications

• FORGED steel, a considerable upgrade. Adopted from the P400 6.5L.

  • Note, cast cranks were still used up to around the year 2020

• Rolled fillets

• One-piece seal rear flange

  • Flywheel bolt torque critical: Max 65 ft/lbs due to rear main seal distortion

1. Various Options

   • Compatible with:

     • Non-turbo applications

       • HMMWV

       • GMT400 non-turbo applications

       • 6.2L replacement/upgrade

     • Side turbo configurations

       • GMT400 Truck, Blazer, Tahoe, Suburban

     • Center turbo setups

       • Hummer H1

       • GMC Savannah

       • Chevy Express

       • Australian GMT400 Suburban

Note: This guide primarily covers the original GM 6.5L diesel engine. The AM General 6500 Optimizer represents a significantly improved version with different specifications and characteristics.