Fig. 40.4
With an aftermarket roller cam it is necessary to install a cam thrust bearing to keep the cam from moving forward. Also you should install a support for the timing cover if using a stock cover because there can be enough force to flex or even bend the stock steel front timing cover, so a support for the front cover can be fabricated (See Fig. 40.4) to hold the cover from flexing. Some aftermarket aluminum water pumps have a threaded boss in the proper location just for this reason.
The clearance between the cam and the thrust bearing should be about 0.002-0.003-inch. This clearance can be checked by installing the cam without the rear cam plug in place.