King AM Aluminum Main Bearing Set (0.75mm Undersize) - NA/NB Miata (90-05)

King AM series main bearing set in the 0.75 mm undersize (King MB5304AM0.75) for the 1.6L and 1.8L engines in the 1990-1997 Mazda Miata (NA) and 1999-2005 Miata (NB). The undersize shells are for a crankshaft whose main journals have been reground 0.75 mm below standard; a crankshaft still at standard size takes the Standard set. The set is five pairs of plain main shells.

• King AM series OE-replacement bi-metal bearing; King describes AM as its standard aluminum-based material and the softest bi-metal in its range
• King lists the AM series for passenger car engines with low to medium loads
• Size: 0.75 mm undersize, for main journals reground 0.75 mm below standard. Have the machinist confirm the finished journal size before ordering
• Set contents: 5 pairs of plain main bearing shells (10 shells), one upper and one lower shell for each of the five main journals
• Dimensions King publishes for this family (standard size): main journal 49.94-49.96 mm, main housing bore 54.00-54.02 mm, shell length 17.5 mm, wall thickness 2.009 mm. King does not publish separate dimensions for each size
• King's size options for MB5304AM: Standard, 0.25mm, 0.5mm, 0.75mm and 1.0mm. Measure the journals and oil clearance before choosing a size; King's catalog does not give a target clearance for this set

Fitment: Main bearings, all five journals. 1990-1997 Mazda Miata (NA, 1.6L and 1.8L) and 1999-2005 Mazda Miata (NB, 1.8L). King's catalog lists this bearing for the Mazda Miata 1.8L (1994-1997 and 1999-2005) and for the Mazda MX-5 1.6L (1989-1994) and 1.8L (1993-2005); the table shows those listings as US model years. King publishes the vehicle list for the MB5304AM family, and this part number is the 0.75 mm size option of that family. King does not list it for the 2006-on MX-5.

Part number: King MB5304AM0.75

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