Wear
I had to go to my personal notes from the Lycoming Service School taught by Jsmes E Doebler in classroom A207, under the Penn State University System in conjunction with Lycoming of Williamsport, PA.
On October 8, 2012:
Serial Numbers: L-12345-67E
L = Lycoming
12345 = sequence
67 = characteristics
E = roller tappets
All Lycoming Engines are now Wide Deck. Roller tappets reduce wear but otherwise do not affect performance.
On a normal engine the cam lobe surfaces are not parallel with the centerline of the cam shaft and the cam followers are convex. Over time the cam follower convex surface becomes spalled. Roller tappets require a different cam lobe profile with a surface that IS parallel with the camshaft centerline. Service Letter SL206 covers field reconditioning of tappet bodies.
Bob Axsom
