Service Instruction No. 1256 F

Valve Guides For Service Use

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Supersedes Service Instruction No. 1256E

April 5, 2012


Intake and exhaust valve guides on all Lycoming engines except as listed below: Intake valve guides only on O-235 and O-290 series unless modified in accordance with the latest revision of Service Instruction No. 1246.


When replacing valve guides

This Service Instruction identifies flanged intake and exhaust valve guides, and respective valve guide drifts, reamers, and gauges necessary to install valve guides on applicable Lycoming engine models.

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