SEAL 1683504 - Caterpillar

3400 Family Of EnginesReference: Engine News, April 1990, "New Valve Lifter Improves Oil Flow To Top Of Engine" for all 3406, 3406B Engines.This article supersedes a previous article with the same title in the April 7, 1982 issue of Engine News on Page 1.
During engine reconditioning or when the rocker shaft assembly is removed, inspect the bridge wear seat to find if the bridge can be used again. Use a dial indicator to measure the amount of wear on the bridge wear seat. Made sure the contact point on the dial indicator is small enough in diameter to get an accurate measurement.
Use the bridge again if the wear is 0.13 mm (.005") or less. See illustration. When the wear seat is worn more than 0.13 mm (.005"), the worn surface of the seat can be ground flat. The maximum amount of material that can be removed is 0.38 mm (.015"). If the seat cannot be made flat, replace the bridge. Reconditioning of the wear seat can only be done once.
Dimensions for reconditioning.