Tri-metal crankshaft main bearings ACL King Nissan RB20 RB25 RB30

The Nissan RB20, RB25 and RB30 inline-six engines

The RB20, RB25 and RB30 are Nissan inline-six engines with a single overhead camshaft and 12 valves, or twin overhead camshafts and 24 valves, naturally aspirated or turbocharged. This page covers the RB20E, RB20DE, RB20DET, RB25DE, RB25DET, RB30E and RB30S, fitted notably to the Nissan Cefiro, Skyline R31, R32 and R33 and Patrol GQ. All these engines share the same crankshaft journal and housing dimensions: the same ACL and King references cover them.

The crankshaft of these engines runs on seven main bearings. Each journal turns between two half shells, one seated in the block and the other in the main bearing cap: they carry the crankshaft. The ACL Race Series and KING RACING tri-metal sets shown here replace them on built engines.

Tri-metal main bearings

A tri-metal bearing stacks three layers: a steel back, a copper-lead intermediate layer with high load capacity and an anti-friction running surface that protects the journal. The complete set covers the seven main bearings of the crankshaft; the King set contains 7 pairs of half shells, including one wider pair for main bearing 4. The upper and lower half shells are different: each goes in its own position.

An aluminium bi-metal takes around 8,000 psi, a performance tri-metal up to 12,000 psi, 50% more. Hence better resistance and better durability on turbocharged, supercharged and high-revving engines.

Technical specifications

Technical guide

The ACL and King main bearings shown here are trimetal bearings, designed for engine building and racing. Compared with an original bearing, they handle far higher loads: they cope with increased power, high rpm or the addition of a turbo or supercharger, where a standard bearing quickly reaches its limit.

The two brands

	ACL Bearing Company, an Australian manufacturer of high-performance engine bearings since 1949, offers with its Race Series precise tri-metal bearings, available in many sizes and proven on built engines worldwide.
	King Engine Bearings, an Israeli manufacturer of high-performance engine bearings since the 1960s, offers with its pMax Black tri-metal alloy bearings designed for heavy loads.

Construction and advantages

Criterion	ACL Race Series	King Racing
Cross-section
Type	High-performance trimetal bearing	High-performance trimetal bearing
Country of manufacture	Australia	Israel
Construction	Trimetal: steel back, copper layer, soft surface	Trimetal: steel back, copper layer, soft surface
Alloy	Race Series (copper-lead)	pMax Black (hardened copper-lead)
Protective coating	No	No
Available sizes	Standard to +0.50 mm (+ increased clearance HX)	Standard, +0.026 and +0.50 mm

Vehicle compatibility

This main bearing set fits the Nissan RB20, RB25 and RB30 inline-six engines (engine codes RB20E, RB20DE, RB20DET, RB25DE, RB25DET, RB30E and RB30S) of the following vehicles: