SL272A Silicone Rocker Box Cover Gaskets Service Letter
All Owners and Operators of Lycoming Aircraft Engines SUBJECT: Release of New Silicone Rocker Cover Gaskets REASON FOR REVISION: Added new silicone gasket part number NOTICE: Incomplete review of all the information in this document can cause errors. Read the entire Service Letter to make sure you have a complete understanding of the requirements.
This Service Letter identifies part numbers for silicone rocker cover gaskets (Table 1) as approved replacements for cork rocker cover gaskets.
NOTICE: A silicone rocker cover gasket can be reused if it is not damaged whereas a single-use cork gasket must be discarded and replaced after it has been removed from the engine.
To prevent leakage, be sure to use the 35 in.-lb. (4.0 Nm) torque value for the rocker cover screws when a silicone gasket is installed and not the 50 in.-lb. (5.6 Nm) torque when a cork gasket is installed.
Service Letter No. L272A (Supersedes Service Letter No. 272) November 21, 2017