Many car enthusiasts consider the camshaft the "brain" of the engine. The camshaft's lobes orchestrate the opening and closing of the valves, which determines the engine's effective rpm range and power band. Replacing the the camshaft on a Chevy 350 engine is a fairly straightforward job, though it will take time, patience, and an understanding of auto mechanics. The specifics vary depending on the model year and design of your engine, but the basics still apply to all of the 350 engines.
Remove the radiator fan shroud. Drain the radiator, unbolt it and remove it. Unbolt the cooling fan from the water pump and pry it off of the pump with a flathead screwdriver. Loosen the alternator and remove the belts. Remove the water pump bolts and pull the water pump off of the engine.
Disconnect the fuel lines, linkages and vacuum lines from the carburetor and intake manifold. Remove the manifold-to-head bolts and pull the manifold off of the heads. Remove the valve cover bolts and pull the valve covers off.
Clear off a clean spot on a large work surface. Unbolt the rocker arms from the heads one at a time. Be sure to keep the rocker arms in order and the nuts with their matching arms. Pull the push rods out as you go and keep them with their matching arms.
Spray all around the lifters with penetrating oil. Grasp each lifter with a pair of channel-lock pliers and pull up while rotating it back and forth and spraying it with oil. Remove all of the lifters and discard them.
Remove the oil pan bolts and drop the oil pan onto the cross-member. Remove the old oil pan gasket and clean the mating surfaces of the block and oil pan with a rag soaked in carburetor cleaner. Remove the bolts from the timing chain covers and pry the cover off of the engine. Unbolt the retaining bolts from the upper timing gear. Grasp the upper cam gear and pull forward. Work the gear and chain off of the crankshaft gear and remove it.
Install a bolt into the threaded hole on the front of the camshaft. Use the bolt as a handle to carefully wiggle the cam out of the block. Take your time to avoid damaging the cam bearings in the block.
Drop your new lifters into a container full of oil to prime them. Rotate the crankshaft so that the dot on the lower timing gear sits at the 12 o'clock position. If you're installing a new timing chain set (as you should), then pull the lower gear off of the crankshaft now. Coat the new camshaft's lobes with chrome-moly break-in lubricant to ensure the lifters break in properly. Coat the cam bearings and gear with assembly lube.
Slide the camshaft into the block. Proceed very carefully and slowly to avoid nicking the bearings. Give the cam a test-spin once you have it in. Wipe the oil off of the flat lower surface of your lifters and drop the lifters one-by-one into the lifter bores.
Install the new timing gears onto the cam and crankshaft, then rotate the cam until the dots on the cam and crankshaft gears line up. Pull the gears back off, slide the chain over them, and push the two gears and the chain onto the engine as a unit. Double-check that the dots are still lined up and re-install the cam gear retainer bolts.
Reassemble the engine in the reverse order of disassembly, using all new gaskets and seals where appropriate. Some engines require that you use sealant around the bolts. Torque values vary by model year and engine.
Turn the engine over either with the starter or by hand until you see the intake lifter on the number one cylinder (front-driver side) begin to rise. Once the intake lifter reaches full lift, tighten the exhaust rocker's nut until the exhaust lifter's plunger just begins to depress. Tighten the nut another half-turn and lock it in place with the jam nut. Repeat this process with the intake rocker, and repeat it 14 more times on all the other rocker arms. Reinstall the valve covers with new gaskets.
Reconnect all of the fuel lines, vacuum lines, electrical connections and linkages. Attempt to start the engine. Don't be alarmed if it doesn't fire up right away. You'll probably need to loosen the distributor bolt and rotate the distributor to adjust the timing. Follow your cam manufacturer's directions to set the timing and break in your new camshaft.
