The Chevy 350 small block engine is a popular engine to make performance upgrades to. Camshaft swaps are one of the more popular upgrades. Whether a cam swap is done for repair reasons or to improve performance, the procedures are generally the same. It requires a good amount of partial engine disassembly, so it's not a simple task. Even for experienced technicians, it takes the better part of a full day, so a do-it-yourself enthusiast may want to plan on taking a full weekend or more to do this correctly.
Drain the coolant. Since engine components that contain water passages will need to be removed, all the coolant has to be removed to prevent it from getting in the engine crankcase. Remove the radiator fan shroud, disconnect the radiator hoses and remove the radiator. This provides more working space, plus it allows enough room to slide the camshaft out of the front of the engine block later.
Loosen all the accessory drive belts on the front of the engine and remove any bolts/brackets attached to the water pump. Remove the water pump and fan. Scrape and clean the gasket surfaces of the water pump and engine block. Rotate the engine to top-dead-center (TDC).
Remove the air intake filter assembly. Disconnect and/or remove all wires, hoses and cables that will interfere with the removal of the intake manifold and carburetor/injection system. Remove the ignition system cap and spark plug wires. Note the position of the distributor housing and rotor on the distributor. (Take a quick picture with a camera phone or draw an illustration to help when reinstalling later.) Remove the distributor. Remove all the intake manifold bolts and lift the intake assembly off the engine. Lay shop rags or paper towels across the valley beneath the intake and clean/scrape away old gasket material. Remove the valve covers. Loosen all the rocker arms and remove the pushrods.
Turn your attention back to the front of the engine. Remove the accessory drive pulley, attach a harmonic balancer puller to the balancer and remove. From underneath the car, loosen and remove all oil pan bolts except the rear two (loosen only), and carefully pry the oil pan down about 1/2 inch. Remove the timing cover from the front of the block. Clean and scrape these gasket surfaces. Remove all the camshaft lifters. Loosen the upper timing gear, slide it off the cam and remove the timing chain. Reattach the camshaft (upper) gear hand-tight. Carefully slide the camshaft out of the engine block while supporting its weight.
Install the new camshaft in the reverse order of removal. Carefully follow all of the manufacturer's instructions for cam installation. Pay particular attention to procedures regarding applying assembly lube to the camshaft bearing journals, lobes and the lifter faces, or camshaft lobe failure may occur when the engine is started.
Begin reassembling the engine in the reverse order of disassembly. Before attaching the intake system and valve covers, set the lifter preload (for hydraulic lifters) according the the cam installation instructions. A harmonic balancer installer is used to reinstall the balancer. Do not hammer it on, or damage to the balancer or crankshaft bearings can occur.
Continue reassembling the engine and reattaching the accessories and components. Refill the engine coolant and follow the instructions for the first start-up of the engine. This is critical. Flat-tappet camshafts must not be operated at below 2000 to 2500 RPM and require operation at this speed to break in the camshaft lobes. Adjust final ignition timing and check for any issues such as leaks, etc.
