Forged connecting rods Honda Acura - 1.8L / 2.0L 16V DOHC - B18 / B20 for forged pistons

The Honda / Acura B18 / B20 engine

Introduced in 1988, Honda’s B-series is a family of double overhead cam (DOHC) 16-valve four-cylinders famous for their strength and tuning potential. The non-VTEC versions covered here are the B18A and B18B (1.8 L, 1,834 cc, 81 mm bore × 89 mm stroke) fitted to the Acura Integra RS / LS / GS, and the B20B and B20Z (2.0 L, 1,973 cc, 84 mm × 89 mm) used in the first-generation Honda CR-V. All are naturally aspirated and produce 126 to 147 hp from the factory depending on the model year.

With a cast-iron block, a counterweighted crankshaft and an aluminium DOHC cylinder head, the B18 / B20 is one of the most popular bases on the Honda scene for turbo conversions, high-compression naturally aspirated builds and engine swaps. The factory forged-steel rods cope with stock use, but become the weak link as soon as boost pressure, engine speed or compression are raised significantly. Replacing the reciprocating assembly with high-strength forged rods is the key step to reliably build a prepared B-Series.

Forged connecting rods

This kit gathers 4 connecting rods forged from 4340 steel, machined from solid then heat-treated to deliver a clear strength gain over the stock rods. You choose the profile (I-HD, three-pocket I-3P or H) and the bolt grade (ARP 2000, ARP L19 or ARP CA 625+) according to your power target and discipline. Each rod is balanced and weight-matched to limit mass scatter and preserve the balance of the rotating assembly.

Designed for both motorsport and sporty road use, these rods suit rally, drift, drag, circuit, hillclimb and time attack. They support Stage 2, Stage 3 and Stage 4 and beyond builds, and are an essential prerequisite once you fit forged pistons, raise the rev limit, increase boost pressure or torque. Depending on the profile and bolts chosen, the set easily handles the power levels targeted by strongly built B18 / B20 engines.

Technical specifications of the B18 / B20 forged connecting rods

Tightening torque and stretch

Connecting-rod bolts can be torqued (without a gauge) or, the method recommended by the manufacturers, tightened by stretch control using a gauge. Stretch control guarantees a consistent preload from one bolt to the next, regardless of thread friction, and is the reference for high-performance use. Always refer to the recommended stretch value shown above for the bolt grade fitted.

Technical guide

4340 forged steel: what is it?

Connecting-rod profiles

	I profile (I-HD): an optimised, reinforced (Heavy Duty) I-beam section. It is the best weight / stiffness compromise, perfectly suited to aggressive naturally aspirated builds as well as moderate to high boost. This is the profile chosen by ZRP and Manley on this kit.
	I-3P profile (Boostline): a three-pocket I-beam geometry (patented three-dimensional body) that stiffens the rod without adding weight. Engineered for high torque and sustained boost, it is the Boostline reference to make a strongly turbocharged B-Series reliable.
	H profile: an H-beam body favouring resistance to bending and compression. Ideal for very high torque and drag use, it offers excellent behaviour under load on the most violent builds. Profile offered in the Manley version.

How to choose your connecting-rod bolts?

The bolts are the most stressed part of the rod: they hold the cap in place on every cycle. NSB Concept offers three ARP grades, from the most versatile to the most extreme, to be chosen according to torque, engine speed and power per cylinder.

	ARP 2000: tensile strength of about 220,000 psi (~1,517 MPa). An excellent performance / versatility ratio, it holds up to roughly 150 hp per cylinder in 5/16" and 200 hp per cylinder in 3/8", at engine speeds up to 8,500 rpm. Suited to circuit, trackday, drift, rally, drag and hillclimb.
	ARP L19: tensile strength of about 260,000 psi (~1,793 MPa). For power and engine speeds beyond the ARP 2000 range. L19 steel is more sensitive to corrosion and hydrogen embrittlement: it must be kept away from moisture and handled cleanly (oiled).
	ARP Custom Age 625+: tensile strength of about 260,000 to 280,000 psi (~1,793 to 1,931 MPa). It is the highest-performing grade, immune to hydrogen embrittlement and with no particular storage constraint, reserved for extreme builds (very high engine speeds and boost pressure).

Measuring bolt stretch

Discover the ARP stretch gauge

The brands offered

	ZRP: rods designed by Alex Drakos (Athens, Greece). Forged from 4340 steel, precision-machined and weight-matched to about ±1 g, they deliver an outstanding performance / price ratio and cover most disciplines (circuit, drift, rally, drag).
	Boostline (Wiseco): a specialist in the three-pocket I-3P profile for strongly boosted applications. Careful manufacturing, a robust pin and a geometry designed to handle high turbo torque.
	Manley Performance (Wiseco group, USA): Pro Series Turbo Tuff rods forged from 4340, weighed and matched, offered in H and I-HD profiles. A historic motorsport reference, renowned for its strength under heavy load.

Glossary

1) Small end 2) Small-end diameter 3) Rod beam 4) Rod bolt 5) Big end 6) Rod nut / bolt 7) Rod cap 8) Big-end diameter 9) Center-to-center

Vehicle compatibility for the B18 / B20 engines

These forged connecting rods fit the Honda and Acura B18 / B20 DOHC non-VTEC blocks listed below. Check the exact engine code of your vehicle before ordering.

OEM reference: 13210-PR4-A00 (set of 4 rods).

Why is it the most economical solution?

When a stock bottom end fails (broken or bent rod, marked big end), fitting stock parts again often reproduces the same fragility, for a comparable cost.

For an equivalent or even lower budget, fitting 4340 forged rods at rebuild time saves you a second strip-down and opens the way to a more ambitious build, with no further parts to change afterwards.

For the same budget: more reliability, more power potential and more longevity. It is the most rational investment for a B18 / B20 meant to last or to gain power.