If you've built many Mopar engines, we're sure you've run into this problem. Once new cam bearings are installed in the block, the cam becomes tight or impossible to install. While at first you might think the cam journals aren't ground properly or the bearings aren't sized properly, the problem usually originates with the block itself. It seems that when the final machine work was performed on most Mopar blocks, especially big-blocks, the cam journals were generally machined to the low end (smallest size) of the acceptable tolerance. So when a new set of bearings is installed, the interference fit is tighter than it needs to be, thereby reducing the inside diameter of the cam bearing. Combine this factor with a new cam that has journals machined to the high end of their tolerance, and installing the camshaft becomes difficult or impossible.

There are a couple of ways to correct this problem in an engine, but only one best way. While we've known engine builders to clearance the cam bearings with a bearing knife (yes, we've even done that ourselves), the proper way to correct this problem is not during engine assembly, but at the machine shop. To show us how to properly hone the block's cam journals, we enlisted Mike Ware of Muscle Motors. Muscle Motors is a leading builder of Mopar engines and has encountered and corrected this problem in numerous blocks. The procedure is pretty simple but requires the right tools and a manual depicting the correct tolerances for the journals. Mike has all the equipment in-house, and quickly showed us the process of correcting the block's cam bearing journal size.

During your next engine build, we suggest you have your machinist check the cam bearing journal dimensions. If your local machinist doesn't have the tools, give Muscle Motors a call. Correcting this problem at the machine shop is far easier than discovering it during engine assembly.

SOURCE
Muscle Motors
2085 Glenn St.
Lansing
MI  48906
5-17/-482-4900
musclemotorsracing.com