RB Swap Guide: Wiring, Fitment, and What to Know Before You Buy

The Nissan RB swap — RB20, RB25, or the legendary RB26 — is one of the most rewarding inline-six builds you can do. It is also one of the most detail-heavy. Here is what to plan for before you buy.

Which RB is right for you?

• RB20DET: the budget entry — smaller displacement, revvy, affordable.
• RB25DET: the sweet spot — more torque, strong stock internals, huge aftermarket. The NEO variant adds refinements.
• RB26DETT: the GT-R icon — twin-turbo, collector value, the ultimate build base.

Wiring and ECU

RB swaps live and die by the wiring. Decide early whether you are running the factory ECU and harness, an adapter, or a standalone engine management system. Confirm the engine you buy includes the harness, ECU, and ancillaries you need — or budget for them.

Fitment basics

RB motors are long. Into an S-chassis (S13/S14) they need swap mounts, crossmember clearance, and often a relocated cooling setup. Confirm transmission compatibility and driveshaft length for your chassis before ordering.

What to verify before buying

• Compression numbers on all six cylinders.
• Turbo condition, and whether turbos are included.
• Exactly what is included: harness, ECU, intake, coil packs, transmission.

Buy your RB in LA

We bring RB20, RB25, and RB26 motors into our Vernon warehouse, compression tested, with drive-in inspection for SoCal buyers. Browse Nissan engines or call (442) 888-0318. New customers: code JDMLA10.