Ditto on the advice about replacing cam & lifters together. When a new cam and lifters are "run in" together, a wear pattern is established that is unique to each lobe/lifter combination. The new cam and lifters should be run at a fast idle, about 2,000 RPM or so, for at least 20 minutes. This allows the new parts to be splashed with lots of oil from the crankshaft while the wear pattern is being established. New lifters are slightly convex, higher in the middle than at the edge, and the cam lobe runs slightly off-center to the lifter. This causes the lifter to spin as it follows the lobe up and down, equalizing the wear. If a lifter wears flat, or gets cupped out in the center, both the cam, and all the lifters should be replaced. Push rods really aren't position-sensitive, just the lifter, which needs to run with the same cam lobe for its entire service life. If the lifter position is changed to a different cam lobe, a new wear-in cycle must happen, which usually results in very rapid cam and lifter wear.
Jerry
