Bulletin: TB2033

Subject: Main Bearing Set

Engine: Ford 351W-351M-400, 1977-79

Clevite Part Number: MS1432P

Explanation:  From time to time we have encountered questions regarding the lug location on the lower flange bearing for these applications. The questions are primarily with the 1978 351M-400 engines. Through 1976 Ford used only a full grooved flange bearing consisting of 2 identical pieces, our MB-2558P. In 1977, Ford went to partial grooved main bearings with a different lug location for all positions. However, the severe duty applications continued to use the full grooved flange bearings because it allowed for a larger volume of oil to flow to the thrust surfaces. The other positions remained partial grooved. During the above mentioned time period, the main caps for position #3 were made with two locating lug notches to permit the engines to be built with either full grooved or partial grooved flanged bearings. This practice continued until 1979 when Ford then reverted back to the use of full grooved flange bearings in all of the engines mentioned above. Ford currently lists only the full grooved flange main bearing, there are no longer any listings for a partial grooved flange for any model year of the above mentioned engines.

All the information we have and the engines we have looked at show that Ford still continues to build these engines with two locating notches in the cap half of the number 3 position. However, on occasion we have had reports from installers who have encountered engines with only one locating notch in the cap half of position #3. As mentioned above these have all involved 1978 351M-400 engines but potentially this could be encountered on any of these engines from 1977-79. If you have a customer who encounters this situation we advise renotching the number 3 main bearing cap to correspond with the locating lug in MB-2558P. We will be adding an Instruction Sheet to these main sets to advise the installers of this procedure should they encounter one of these engines with only one locating notch.