Is this a not so uncommon problem?

[Galtmn]

All of a sudden while driving I start hearing a ticking valve train (assumed) noise. Also the exhaust sound changed to (another assumed) sound of not firing on all cylinders.
Got it to my mechanic and in about 15 minutes he found the problem...a broken bolt that secures the rocker shaft on the driver side. (Aluminum heads, roller rockers). There were also some broken helicoil threads coming out with it. Apparently that is a standard procedure to utilize helicoils in this application into the aluminum heads...?

 

[Nick Micale]

Never seen a broken rocker bolt, but many bolts/stud have pulled out of alum heads.

On my early personal alum heads, I had helicoils installed for all the rocker studs before I ever installed them.

On the TA alum heads, this is not an issue as the rockers are bolted to a steel stand which is first fastened to the head.