The dual overhead camshaft, or DOHC, consists of a two-shaft system that sits on top of the cylinder head. It is not difficult to change the camshaft, but the project will take several hours. Consider changing both shafts if you are going to change one, simply because you will end up doing the job again at some point. Make sure the replacement camshaft(s) are specific, to either the exhaust side or intake side. This article is based on the 1.8L Nissan engine, but the procedure is similar for most vehicles with DOHC.
Disconnect the battery by removing the negative cable with a socket and ratchet . Open the valve on the bottom of the radiator using a wrench. Drain the engine coolant into the drain pan. Relieve the pressure from the fuel system by opening the valve on the fuel rail. Remove the accessory drive belts from the engine. Disconnect the exhaust pipe from the manifold using a wrench.
Remove the power steering pump and bracket using a socket and ratchet to loosen the bolts. Remove the cylinder head cover using a socket and ratchet to loosen the bolts. Remove the distributor cap by loosening the screws with a screwdriver. Mark the rotor position in relation to the distributor and remove it.
Remove the distributor from the engine by loosening the bolts with a wrench. Remove the timing chain tensioner using a socket and ratchet. Remove the sprocket from the camshaft. Be sure to note the position of the camshaft because you will have to put the new one(s) in the exact same way.
Remove the camshaft bearings center caps, and work your way out using a socket and ratchet. Note the position of each bearing cap. You must install them the same way they came off. Remove the camshaft(s) from the engine. Put the new shaft(s) in and coat it with engine oil. Replace the bearing caps the same way they came off.
Install the bearing cap bolts and torque them to the following specs, making sure the camshaft(s) is/are in the proper positions as when they came off.
First pass bolts 11-15 to 18 inch-pounds and then bolts 1-10 to 18 inch-pounds
Second pass bolts 1-15 to 53 inch-pounds
Third pass bolts 1-14 to 87-105 inch-pounds
Last pass bolt 15 to 56-73 inch-pounds
Install the sprocket and timing chain. Install the bolt and tighten it with a socket and ratchet. Hold the other end of the camshaft with a wrench while you tighten the bolt. Install the timing chain tensioner and tighten the bolts with a socket and ratchet. Install the distributor according to the alignment marks and tighten the bolts with a wrench.
Install the rotor button according to the alignment mark. Install the distributor cap and tighten the securing screws with a screwdriver. Install the cylinder head cover and tighten the bolts with a socket and ratchet. Install the power steering pump and bracket using a socket and ratchet to tighten the bolts.
Connect the exhaust pipe to the manifold and tighten the bolts with a wrench. Install the accessory drive belts and route them according to the diagram under the engine hood. Connect the negative battery cable and tighten the nut with a wrench. Refill the radiator and reservoir with coolant.
