CAMSHAFT AS 1278841 - Caterpillar

All 3400, 3500, 3600 Series Industrial, Marine and Generator Set EnginesSUPPLEMENT: 06/00/86ENGINE NEWS, APRIL 1986, PAGE 3, "Adjust Bridge Whenever Valve Clearance Adjustments Are Made".Put a mark through the second sentence of the first paragraph. The sentence should read: Put a mark through the ONLY and make a note in all applicable publications, that the bridge should be adjusted EACH time valve clearance is adjusted.
--------------- END SUPPLEMENT ---------------At the present time, many service publications (Service Manuals, Operation & Maintenance Guides etc.) for the above engines contain a note that recommends the valve bridge be adjusted ONLY if a valve has been replaced, ground or the cylinder head has been reconditioned. Put a mark through the ONLY and make a note in all applicable publications, that the bridge should be checked and/or adjusted EACH time valve clearance is checked and/or adjusted. Valve and valve mechanism components do not always wear evenly, which can allow the bridge to go out of adjustment. Caterpillar now recommends that the bridge ALWAYS be checked and/or adjusted when a valve clearance adjustment is made.
It is not necessary to remove the rocker arm shaft to adjust the valve bridges, but there must be valve clearance. Push on the top of the rocker arm directly above the center of the bridge to check bridge adjustment. Use the step-by-step instructions given in the Service Manual to make the bridge adjustments. Make a note that at all scheduled maintenance intervals, whenever a valve clearance adjustment is made, the valve bridges must be adjusted.