Series 60 Failure Analysis Valves

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Amanda Lee
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1 Series 60 Failure Analysis Valves Rev. Date

This information is intended to provide training on proper identification of failure modes associated with valves and the valve train on S60 engines.

2 This information is intended to provide training on proper identification of failure modes associated with valves and the valve train on S60 engines. In addition, this information will outline Warrantable vs. Non-warrantable failures that are currently being reviewed through return material inspections. DDC is committed to providing a continuously improved product, and through proper component diagnosis, DDC will continue to provide product improvements for the future. Valve Combustion Face Identification Exhaust Valves H S60.026" "I" - Intake "E" - Exhaust U S60.020" E J G & 60G.036" Green U Marine.028" Pink Only valves used on Off-Highway engines have the numbers stamped into the combustion face. All valves have the tip identification. Intake Valves E On-Highway 0.026" S50, " I I A J G & 60G.011" White S50 & 60 Marine.008" Blue On-Highway 0.008" " DePentu 29 Jan E8 Valve Tip Identification Fillet Blend Head Stem Weld

Camshaft timing, overhead adjustment, engine brake setting, and worn parts are the greatest contributors to valve failure.

3 Valve failures may look like the primary cause of the engine failure, however in most cases the valves are in fact secondary failures. To perform a proper analysis it is necessary to pay close attention to all other components of the valvetrain during disassembly. Camshaft timing, overhead adjustment, engine brake setting, and worn parts are the greatest contributors to valve failure. Events that cause valve failures Piston to valve contact in a single cylinder A single cylinder with piston to valve contact is usually an indicator of misadjusted overhead or some other failed component causing the valve to be held open. Valves will never touch the piston under normal conditions. Possible causes Broken overhead parts Broken injector spring Valve material defect Negative lash Malfunctioning engine brake components Broken Overhead Spring Example of a broken injector spring that lodged into a valve spring and caused considerable collateral damage. These types of failures are usually warrantable unless the failure is associated with a prior repair within ninety days, and then the failure would be considered to be workmanship related.

Piston to valve contact in all cylinders If the piston to valve contact failure is caused by a camshaft timing issue then evidence of valve contact

This situation has been found most frequently after some other repair has been done to the engine that required disturbing the camshaft to cam gear hub

Improper cam gear timing Improper cam bolt torque Misalignment of cam dowel pin Reuse of cam bolt Loss of cam timing due to improper cam bolt torque that

Note: Repair facilities with the best success at performing cam and hub assemblies without errors have adopted the two person verification of the gear

4 Piston to valve contact in all cylinders If the piston to valve contact failure is caused by a camshaft timing issue then evidence of valve contact should show on several pistons. This situation has been found most frequently after some other repair has been done to the engine that required disturbing the camshaft to cam gear hub joint, and the reassembly procedures were not performed correctly. Improper cam gear timing Improper cam bolt torque Misalignment of cam dowel pin Reuse of cam bolt Loss of cam timing due to improper cam bolt torque that resulted in valve to piston contact on several pistons and valve drop in one cylinder. Cam seals were recently changed prior to this failure. Note: Repair facilities with the best success at performing cam and hub assemblies without errors have adopted the two person verification of the gear timing and cam bolt torque. This would require the shop supervisor to confirm the gears are marked and locked prior to disassembling, returned to the same marks during assembling, and witnessing the new cam bolt being properly torqued. This type of failure is most often considered non-warrantable unless there has been a minimum of ninety days from any associated prior repairs.

Valve Stem Fatigue Valve stem fatigue could occur without any impact damage, and usually the straightest valve stem was the first valve to

Fail Valve Head Failure Valve head failure is usually due to excessive wear or the improper valve to valve seat relationship.

Worn guides may cause turned edges of the valve from contact with the liner.

5 Valve Stem Fatigue Valve stem fatigue could occur without any impact damage, and usually the straightest valve stem was the first valve to fail. The other valves in the same cylinder will have bent stems from impacting the head of the prior valves that failed and got trapped between the piston and cylinder head. Poor seating imparts bending load Worn guides Temperature induced wear Mechanical induced wear Lack of lubrication Valve deflection First to Fail Valve Head Failure Valve head failure is usually due to excessive wear or the improper valve to valve seat relationship. Excessive lash will lead to valve pounding, while lack of lash may cause torching. Worn guides may cause turned edges of the valve from contact with the liner. Excessive lash Pounding Excessive seat runout Excessive guide runout or worn guide Debris between valve and seat Overspeed high closing velocities Rocker shaft bushing wear (increases lash and closing velocity) Torching Caused by worn guides allowing contact with liner Stem fatigue and valve head failures are may or may not be warrantable base on general wear condition and age of the components.

A Tech 2 will not positively enable you to identify the use of a power-up device.

A Tech 2 will not positively enable you to identify the use of a power-up device. Aftermarket power-up devices are non-approved by General Motors. These devices are usually piggy-backed in the main engine harness or remain connected to the diagnostic connector to upload the calibration