Why is the use of a stranded camshaft bearing driver and hammer not recommended for aluminum heads?

• A. They may damage the camshaft lobes
• B. They may bend the connecting rod
• C. They may break the aluminum bearing supports
• D. They may cause valve seats to loosen

Answer: (C)

The main idea here is that aluminum heads have cam bearing supports made of softer material, and they can be damaged by impact. A camshaft bearing driver used with a hammer delivers concentrated percussive force to install the bearing. In an aluminum head, that force can deform, or even crack, the bearing supports and their bores. Once those supports are damaged, the cam bearings won’t sit true, oil clearance can be affected, and you may end up with leaks or cam timing issues. That’s why this method is not recommended.

The other options don’t fit the situation as well. Hitting the cam lobes directly isn’t the goal of installing bearings, and a connecting rod is part of the crankshaft, not the cam bearing installation. Valve seats aren’t the target here either, so they’re not the primary failure mode from using a hammer with a bearing driver in an aluminum head.