Trimetal connecting rod bearings ACL Nissan CA16 CA18 CA18DET CA20

The Nissan four-cylinder CA16, CA18 and CA20

Built from 1982 to 1994, the CA family is Nissan's compact four-cylinder petrol engine: cast iron block, aluminium head and belt-driven camshafts. It comes in 1.6, 1.8 and 2.0 litres, from the single overhead cam eight-valve to the twin-cam sixteen-valve. The CA18DET is its most highly developed version, 1809 cc, 83 mm bore and 83.6 mm stroke, Garrett T25 turbocharger and intercooler, for 169 hp and 228 N·m. All of them share the same crank pin: a single bearing set covers the family, from the carburetted Bluebird to the 200SX RS13-U.

From the factory these engines are fitted with connecting rod bearings graded 0, 1 and 2, matched to the crank pin grade stamped on the crankshaft and identified by a colour mark: no mark for grade 0, brown for 1, green for 2. Their wall thickness runs from 1.501 to 1.510 mm depending on grade, and the workshop manual holds them within a clearance window of 0.018 to 0.045 mm, with a wear limit of 0.100 mm. For service Nissan offers only three undersizes, 0.08, 0.12 and 0.25 mm. As soon as power, engine speed or boost pressure rise, this production design reaches its limit.

Trimetal connecting rod bearings

A tri-metal bearing stacks three layers: a steel back, a high load capacity copper-lead intermediate layer and an anti-friction running layer that protects the crank pin. The complete set contains 8 half-bearings, four pairs for a four-cylinder engine.

Tri-metal is designed for high, sustained loads, where an aluminium bi-metal works at low to medium loads: 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

Running clearance

Running clearance is the gap between the bearing and the crank pin in which the oil film circulates. In operation the crank pin does not rub on the bearing: it runs on that oil film, which carries the load. The clearance sets the thickness of that film: too tight and the oil flows poorly, temperature rises and the risk of seizure increases; too loose and the oil escapes, the film loses its carrying capacity and oil pressure drops. The right clearance is the balance between sufficient lubrication and a well maintained oil film.

Check on assembly: lay a measuring strip on the crank pin, tighten the rod cap to the specified torque, then compare the crushed width against the scale to read the clearance.

Connecting rod bolt torque

The Nissan workshop manual requires the threads and seating faces of the original (OEM) bolts to be oiled before tightening. On forged rods, ARP recommends the stretch method (gauge).

Technical guide

The ACL connecting rod bearings shown here are tri-metal bearings, built for engine building and racing. Compared with the production bearing they take far higher loads, and above all they offer a choice of sizes the manufacturer does not: a standard size, a +0.025 mm size for a crank pin that has merely been polished, two regrind sizes at +0.25 and +0.50 mm, and an HX version with extra clearance for engines that rev hard or need a high oil flow. That choice is what lets you match a reworked crankshaft without changing range, and tune the clearance to the oil and the use intended.

The brand

ACL Bearing Company, an Australian maker of high performance engine bearings since 1949, offers with its Race Series precise tri-metal bearings, available in many undersizes and proven in built engines worldwide.

Vehicle compatibility

Original part numbers : 12111-16A00, 12111-D0200, 12111-D0210, 12111-D2800, 12111-D4200, 12111-V5500. Set graded by class 0, 1 and 2 according to the crank pin grade.

Why replace the bearings

A connecting rod bearing that fails does not stop at itself: it scores the crank pin, sends its debris into the oil circuit and calls for a crankshaft regrind at the very least, when it does not take the rod and the block with it. On a built CA engine the bearing set costs a fraction of a regrind, and far less than a rebuilt engine. It is the cheapest part of the rotating assembly and the one whose failure costs the most.

Fit at the same time

A crankshaft that is out is the opportunity to go through the whole rotating assembly. The forged connecting rods and forged pistons for this engine fit in the same job, with no extra stripping.