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Camshaft wear in high mileage engines is a common problem, so inspect the cam carefully to see if it is worn or bent. If the engine needs a new cam, you can install a stock replacement cam or a performance camshaft. Performance cams provide increased lift and duration for more power. If you opt for a hotter cam, be sure to follow the camshaft supplier application recommendations for lift and duration. A common mistake is overcamming a street engine. Too much lift and duration will move the engine's power curve too far up the rpm scale, and may require other extensive modifications such as larger valves, stiffer valve springs, performance manifolds and modifications to the carburetor or fuel injection system to optimize performance.
When a cam is being replaced, new lifters and valve springs should also be installed. Reusing old lifters with a new cam can damage the cam lobes.
Roller lifters can generally be reused, but not on a camshaft designed for flat bottom (actually slightly convex) lifters (and vice versa).
In addition to a new cam, the engine may also need a new timing belt or chain and gear set. The recommended replacement interval for timing belts on most older engines (those made before 1993) is 60,000 miles. The replacement interval for many newer belts has been increased to 100,000 miles. Timing chains have no specified replacement interval, but do stretch with age. This has an adverse effect on valve timing as well as ignition timing, so the chain and gears should be replaced if wear exceeds specifications.
Engine Rebuild Tutorial Links:
When a cam is being replaced, new lifters and valve springs should also be installed. Reusing old lifters with a new cam can damage the cam lobes.
Roller lifters can generally be reused, but not on a camshaft designed for flat bottom (actually slightly convex) lifters (and vice versa).
In addition to a new cam, the engine may also need a new timing belt or chain and gear set. The recommended replacement interval for timing belts on most older engines (those made before 1993) is 60,000 miles. The replacement interval for many newer belts has been increased to 100,000 miles. Timing chains have no specified replacement interval, but do stretch with age. This has an adverse effect on valve timing as well as ignition timing, so the chain and gears should be replaced if wear exceeds specifications.
Engine Rebuild Tutorial Links:
