Something that many people take for granted is checking the camshaft end play (especially on flat-faced lifter camshafts) when assembling their engine. In most instances, the lifters will bear against the taper that is ground into each lobe, locating the camshaft to the rear of the engine, as intended. However, there are a number of other factors that must be considered and should always be checked for good performance and longevity.
When building a fresh engine with new cam bearings, the cam end plug has been removed, and a new one should have been installed. If the end plug is now located too far forward in the block, the end of the cam may now be bottoming out on the plug, causing the lobes to be improperly aligned with the lifters. It will also cause the timing sprockets to be out of line. This will cause premature cam and lifter wear, and will damage the timing chain and sprockets. Make sure that the cam sprocket is able to ride against its correct thrust surface and that the cam and crank sprocket are in alignment when installed on your camshaft. On engines that may have a cam thrust plate (Ford FE, Chrysler LA 273-360, etc.), clearance to the end plug must also be checked. If the plug is too far forward when the plate is tightened, the back of the cam could now be forced against the rear plug. Galling will occur, heat will be generated, and unhappy metal particles may be passing through your powerplant. Also, camshafts from different manufacturers may have slightly different lengths, so don’t assume that if one cam fits properly, others will as well.
On thrust plate equipped engines, plates may vary slightly in thickness, and the steps on the cam and cam sprocket can also vary. Make sure that you don’t have a stack-up of tolerances that could prevent the cam from rotating freely. Install the cam, thrust plate, and sprockets without the timing chain to verify that nothing is in a bind. You should have approximately .003-.005″ of end play to allow for thermal changes and to promote proper lubrication in the thrust area. Engines that have roller camshafts installed (that didn’t originally have them) may require an aftermarket cam button spacer or some other type of device to keep the cam from moving forward (roller camshafts have no lobe taper). A slight amount of end play is also required for proper function. If possible, leave the cam end plug out until final assembly. This way, you can check end play once the front cover has been installed, its gasket crushed, and all tolerances taken up. With a dial indicator riding against the rear of the cam, reach through the lifter bores and move the cam back and forth. The .003-.005″ end play dimension should be maintained. When installing the cam end plug, be careful not to drive it in too far, undoing all of the work you’ve done up to this point.
There are many configurations and methods that manufacturers have used to locate their camshafts properly. It would be impossible to list all of them here. Just be sure to check the basics of proper cam alignment, end play, and free rotation. If you aren’t sure that what you have is correct, consult a shop manual, or someone familiar with your type of engine and application.