3976339 Piston rings for Cummins ISBe ISDe QSB6.7 Replace No.4932801

Cummins 3976339 Piston Ring Set

Replacement for: 4932801 (superseded part)
Compatible Engines:

• ISBe (4.5L & 6.7L)

• ISDe (6.7L)

• QSB6.7 (Marine/Industrial)

Technical Specifications

1. Set Contents

• Top Ring: Ductile iron with molybdenum plasma coating

• Second Ring: Tapered/scraper design with phosphate treatment

• Oil Ring: 3-piece design (chrome-plated steel rails + expander)

• Quantity: Full set for 1 cylinder

2. Critical Dimensions

3. Material & Coatings

• Top Ring: High-strength steel with anti-wear coating

• Oil Ring: Stainless steel rails for corrosion resistance

Key Features

✔ Reduced Oil Consumption: Optimized rail tension
✔ Extended Life: Hardened coatings resist cylinder wear
✔ Improved Sealing: Gas-ported top ring design (ISDe models)

Compatibility Notes

• Fits Both: Standard and oversize pistons (mark “OS” for oversize)

• Not for: QSL9 engines (different bore size)

Installation Guide

1. Preparation:

   • Hone cylinders to RA 0.4–0.6 μm finish

   • Clean ring grooves with a dedicated tool

2. Staggering:

   • Offset ring gaps 120° apart

   • Avoid aligning gaps with piston pin or thrust sides

3. Torque Values:

   • Connecting rod bolts: 90 Nm + 90° turn (ISBe)

Warning

⚠ Critical Checks:

• Measure ring-to-groove clearance (max 0.08 mm)

• Never reuse old rings or install on scored pistons

• Use Cummins-approved assembly lube

Replaces Obsolete Parts

• 4932801 (older design)

• 4085643 (pre-2010 engines)

Cross-Reference

Need the cylinder honing specs or break-in procedure? Ask for details!

Maintenance Tips

• Break-In: Run at varying loads for first 50 hours

• Inspect: Check oil consumption every 250 hours

• Expected Life: 12,000+ hours with proper maintenance