How to Swap a RB25 With a 240SX
The RB25 six-cylinder engine produces 250 horsepower, compared to 150 horsepower delivered by the stock Nissan 240SX four-cylinder engine. RB25 and RB25 DET engines are designed for installation in the 240SX engine compartment. In addition, the engines are available with compatible bell housing mounts for Nissan’s KA, CA and SR transmissions used in the 240SX. Swapping the engines requires mechanical expertise, a full set of tools and portable equipment. RB25 engines are available through speed shops. The equipment can be purchased or rented at auto parts stores.
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Things You'll Need
- Metric tools
- Pry bar
- Screwdrivers
- Utility pan
- 1/2-inch hoisting chain
- Rolling engine hoist
- Rolling transmission jack
- Engine stand or wood pallet
- RB25 exhaust headers with gasket and pipe clamp
- Bell housing gasket
- Coolant
- Engine oil
Instructions
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Pulling the 240SX Engine
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1
Remove the engine hood from its hinges and set the hood aside. Disconnect the battery cables and remove the battery from the engine compartment. Detach the engine wire connectors from the ECU module.
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2
Remove the coolant filler cap. Open the petcock at the underside of the radiator and drain the coolant into a utility pan. Detach and remove the upper and lower radiator hoses. Remove the fan shroud, electric cooling fan and the fan belt. Remove the radiator from the engine compartment.
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3
Disconnect the throttle linkage and fuel line from the carburetor. Disconnect the heater hoses from the fittings at the firewall. Detach and remove all vacuum lines and recirculation hoses from the intake manifold and engine block.
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4
Detach and remove the four-cylinder exhaust headers from the exhaust manifold and the muffler pipe. Discard the exhaust gasket. Loosen and remove the motor-mount bolts at the underside of the engine on each side.
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5
Remove an intake manifold bolt at the front and rear of the engine. Attach the ends of a 1/2-inch hoisting chain at the front and rear of the engine with the bolts. Position the arm of an engine hoist above the center of the engine. Hook the middle of the chain onto the hook at the end of the arm. Raise the hoist just enough to tighten the chain, without lifting the engine off the motor mounts.
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6
Disconnect the shifter linkage at the transmission. Position a rolling transmission jack firmly against the underside of the transmission. Loosen and remove the bell housing bolts at the front of the transmission. Roll the jack and transmission toward the back of the car until the transmission disengages from the engine shaft at the face of the transmission.
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7
Raise the hoist arm as you guide the 240SX engine up and out of the engine compartment. Steady the engine to prevent it from swinging on the chain as you roll the hoist away from the car. Mount the engine on an engine stand or lower it onto a wood pallet. Detach the hoisting chain from the engine.
Installing the RB25
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8
Connect the ends of the hoisting chain at front and rear of the RB25 intake manifold with the respective manifold bolts. Position the hoist at the front of the engine, and attach the chain to the arm. Raise the hoist arm and roll the hoist toward the front of the car as you position the engine above the engine compartment.
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9
Lower the hoist arm slowly as you align the motor mounts at the underside of the engine with the mounts on each side of the engine compartment. Install the original motor-mount bolts at each mount. Lower the hoist arm and remove the chain from the manifold. Reinstall the manifold bolts.
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10
Fit the bell housing gasket on the studs at the face of the housing. Roll the transmission jack and transmission forward, toward the rear of the engine. Align the engine shaft with the port at the face of the transmission, and push the transmission against the engine. Secure the attachment with the original bell-housing bolts. Remove the jack. Reconnect the shifting linkage to the transmission.
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11
Include the new exhaust manifold gasket as you attach the six-cylinder RB25 exhaust headers at the exhaust manifold with the provided bolts. Attach the open end of the main header pipe to the original muffler pipe with the provided clamp.
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12
Connect the end of the original throttle linkage to the throttle arm on the fuel-injection manifold. Secure the shaft of the linkage into the provided clamp at the rear of the throttle arm. Attach the end of the original fuel line to the brass fitting on the fuel injector pump. Connect the RB25 engine-wire connector to the ECU module.
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13
Reinstall the radiator and the original radiator hoses. Install the original electric cooling fan and fan shroud. Fill the radiator with properly prepared coolant. Fill the engine with oil. Reinstall the battery and connect the battery cables. Reattach the engine hood to the hinges.
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1
Tips & Warnings
Include new oil and fuel filters and replace any worn belts or hoses during the RB25 installation.
Always use the recommended engine oil.
Set the ignition timing with a strobe timing light or electronic interface machine.
For racing applications, remove the stock muffler and exhaust pipe and install a racing exhaust pipe to reduce engine back pressure.
It might be necessary to reconfigure or retrofit the vacuum lines and exhaust re-circulation hoses for connection at the engine and fuel injection manifold.
These procedures are meant as a general guide only. It is the responsibility of the mechanic to evaluate all aspects of the engine swap in detail beforehand.
References
Resources
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