It is assumed that the engine is already out of the vehicle and the rocker arm cover has been removed, as this procedure cannot be performed with the engine installed. Once lobe lift has been determined, the pushrods, pushrod cover, valve lifters, distributor, oil pump driveshaft, front pulley and hub, and timing gear cover must be removed before the camshaft can be extracted. Camshaft lobe lift is a critical inspection procedure that should be conducted before removing the head from the engine. Lobe lift is typically measured by placing a dial indicator atop the cylinder head next to each pushrod and measuring the rocker arm's movement as it is pushed upward by the pushrod and cam lobe. Starting with the number one cylinder, mount a dial indicator with the stem resting on the rocker arm, aligned with the exhaust valve pushrod. Rotate the crankshaft slowly in the normal running direction until the lifter stem is on the heel of the cam lobe, at which point the pushrod will be at its lowest position. Zero the dial indicator, then slowly rotate the crankshaft until the pushrod reaches its highest position, noting and recording the reading on the dial indicator for comparison with lobe lift specifications. Repeat this for each remaining valve, and if the measurements do not meet specifications, a new camshaft should be installed. For a four-cylinder engine, remove the camshaft thrust plate screws/bolts by rotating the camshaft until the access holes in the timing gear align with them, then extract the camshaft and timing gear through the front of the block, taking care to avoid damaging the camshaft bearings. If the timing gear needs to be removed from the camshaft, it must be pressed off using a hydraulic press; if unavailable, take it to an automotive machine shop. Before installing the camshaft, coat each of the lobes and journals with engine assembly lube or moly-base grease, then slide the camshaft into the engine block, ensuring not to damage the bearings and aligning the marks on the gears. For a V8 engine, after removing the valve lifters, crankcase front cover, timing chain, and timing sprocket, detach the camshaft rear cover and use a long bolt in one of the camshaft bolt holes for support during removal. Carefully pull the camshaft out of the engine block, ensuring not to damage the camshaft bearings, and before installation, coat the lobes and journals with engine assembly lube or moly-base grease, sliding the camshaft into the engine block while supporting it with wire to prevent bearing damage.
Posted by GMPartsGiant Specialist