Camshaft "Break-in"If the camshaft and lifters feature a flat-tappet (solid or hydraulic) design, camshaft break-in is absolutely critical to camshaft longevity. It's also important to make every effort to ensure that the engine will start during the first attempt.
Once the engine has fired, keep it running and immediately bring engine speed to within 1,500-2,200 rpm, especially if a flat-tappet cam and lifter system is employed. Maintain engine speed within that range, varying up/down, for about 20 minutes. This will help to properly "seat" rings, bearings, and the camshaft/lifters. If an engine with a flat-tappet camshaft and lifters is operated below about 1,500 rpm during the initial run, there may not be sufficient oil lubrication to the cam lobe/lifter contact areas to allow the lifters to rotate.
Increased oil pressure resulting from elevated engine speed helps the lifters to rotate, rather than scuffing against the lobes in a locked (non-rotating) position. If the lifters are not lubricated properly and don't rotate during this first run, they can initiate a wear path at the lobe, which will quickly damage the cam lobe(s). "Don't kid yourself about this," says Schaerer. "If the engine is insufficiently lubricated at the lifter-to-lobe contact area, you can cause permanent damage to the lobes and lifter within a few seconds of startup, and you can destroy a flat-tappet camshaft and its lifters in less than a minute."
If the cam and lifters are of the roller design, where each lifter features a roller bearing at its camshaft lobe contact, camshaft break-in is much less demanding (some will argue that roller cam break-in is simply a non-issue). That's because instead of the lifters scuffing across the cam lobes while trying to establish a mating pattern, roller lifters "roll" across the lobes, virtually eliminating any lobe/lifter frictional mating concerns. Nonetheless, it's still wise to elevate the initial run for a few minutes, even when dealing with a roller cam setup, if only to ensure that the oil pressure is sufficient to aid in the lifter roller-tip operation.
Clevite's Schaerer offers this final bit of advice, "The golden rule that applies to starting up a fresh motor is simple: Slow down and take your time in carefully performing a complete pre-flight check. Remember, any extended period of cranking can cause oil to be wiped from critical load bearing surfaces, such as cam lobes and lifters. The goal is to achieve smooth engine startup on the first try."