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Cummins ISX Counterbore Shimming Procedure: ATCISX20 .020″ Brass Shim Professional Guide

Detailed shimming procedure for Cummins ISX using ATCISX20 .020 brass shim.

ATCISX20 Cummins ISX counterbore shimming procedure step-by-step

By Blog Admin • January 11, 2026 • Posted in Diesel Tools, Products

This 12-phase procedure uses the ATCISX20 .020″ brass shim to correct counterbore depth in Cummins ISX engines. Ensures proper liner seating and protrusion for leak-free, high-compression performance in heavy-duty rebuilds.

Introduction: Essential Shimming for ISX Rebuilds

Correct counterbore depth in Cummins ISX is vital for liner sealing. The ATCISX20 shim compensates for wear/machining, restoring OEM specs to avoid failures—key for durable rebuilds.

Phase 1-3: Block Preparation & Measurement

Remove old liner and clean bore – Inspect for cracks
Measure counterbore depth – Use micrometer; note deviation
Select .020″ ATCISX20 shim – Verify thickness
Place shim in counterbore – Center evenly
Install new liner dry – Check initial protrusion

Phase 4-6: Liner Seating & Protrusion Check

Seat liner with installer tool – Apply even pressure
Measure protrusion with gauge – Aim for 0.004–0.006"
Adjust if needed – Add/remove shim as required
Verify flush sealing – No gaps around liner
Repeat for all cylinders – Maintain consistency
Document depths per bore – For records

Phase 7-9: Assembly & Torque

CRITICAL: ATCISX20 Shim Setup

Install pistons/rings – Torque rods
Reassemble head/gasket – Align properly
Torque headbolts in sequence – To Cummins spec
Check for compression even – Use tester
Inspect shim integrity – No deformation
Prime oil system – Before start

Phase 10-12: Testing & Finalization

Refill fluids and start engine – Idle leak test
Road test under load – Monitor temp/pressure
Re-check protrusion after run-in – Confirm stability
Update service logs – Note shim used
Schedule follow-up – At 1,000 miles

Critical Safety Warnings: Shimming Procedure

MUST AVOID THESE FATAL ERRORS:

❌ Never skip measurement – Wrong protrusion leaks ($1K+)
❌ Never force liner – Cracks shim/block
❌ Never dirty bore – Contaminates ($3K+)
❌ Never uneven seat – Causes hot spots
❌ Never omit gauge – Inaccurate protrusion
❌ Never reuse worn shim – Fails sealing
❌ Never skip test – Hidden issues
❌ Never ignore PPE – Heavy parts injure

Professional Rebuild Documentation

Service Phase	Documentation Required	Complete?
Pre-Service	Bore depth measures, shim thickness	□
Seating	Initial protrusion, pressure applied	□
Assembly	Head torque sequence, final protrusion	□
Testing	Leak check, compression readings	□
Final Approval	Signature, warranty notes	□

Why ATCISX20 Outperforms Standard Shims

Risky Standard Methods:

❌ No shim → Leaks ($1K+)
❌ Wrong thickness → Hot spots
❌ Steel shim → Poor sealing
❌ Uneven install → Contam
❌ Manual fix → Rebuilds

ATCISX20 Advantages:

✅ .020" precision
✅ Brass malleable seal
✅ Protrusion restore
✅ Leak prevention
✅ Protects $7,500–$15,500
✅ Corrosion resistant
✅ Compression even
✅ OEM spec

Shim Professionally. Secure ISX Blocks. Maximize Durability.

Get ATCISX20 – $40.00

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