This guide outlines the process of swapping a D16Z6 (OBD1 SOHC VTEC) engine into a 4th-generation Civic or 2nd-generation CRX (OBD0 chassis).

Mechanical Installation#

Installing a D16Z6 is very similar to an A6 swap, with minor adjustments required:

• Driver's Side Engine Mount: The A6 mount is wider. You can reuse the A6 mount, though minor grinding of the metal may be required to prevent the timing belt from brushing against it.
• Crankshaft Pulley: Use the D16Z6 pulley, as it is balanced specifically for the Z6 crankshaft.
• Manifolds: Using the Z6 intake and exhaust manifolds is highly recommended for optimal performance. The Z6 intake is ported specifically for the engine's flow characteristics, and the Z6 4-2-1 exhaust manifold outperforms the A6 4-1 manifold.
• Clutch/Flywheel: Use the flywheel and clutch assembly appropriate for the transmission you are using. Note that 88-year models have a different input shaft spline count, requiring specific clutch discs.

Wiring & Electrical Conversion#

Sensor Relocation#

• MAP Sensor: On the 93-95 Z6, the MAP sensor is located on the throttle body. You must extend the MAP sensor wiring from the firewall (OBD0 location) to the throttle body (OBD1 location).
• Coolant Temperature Sensor: If using a 93-95 Z6 engine, the sensor is located on the thermostat cover and will require wiring relocation from the back of the block (OBD0 location).

Distributor Modifications#

The Z6 distributor mounts do not align perfectly with the OBD0 head.

• The top and bottom-right mounting legs will be used.
• The bottom-left leg will likely require enlargement or cutting to fit correctly.
• Use large washers to ensure the distributor makes positive, flat contact with the cylinder head.
• Note: Use Z6 spark plug wires and a new distributor O-ring to prevent oil leaks.

Fuel System#

• Injectors: Use the A6 injectors with your stock OBD0 ECU (PM6).
• O-Rings: Replace all fuel injector O-rings to prevent fire hazards.
• DPFI to MPFI: If your chassis was originally a Dual Point Fuel Injection (DPFI) model, you must convert the car to Multi-Port Fuel Injection (MPFI) before this swap will function.

VTEC Activation#

To enable VTEC, you must wire an activation trigger.

• Simple Approach: Use an RPM-activated switch or adjustable shift light.
• Optimal Approach: Convert to an OBD1 ECU (using a custom harness or ECU conversion) to leverage factory VTEC control logic and optimized fueling maps.