I think these are some of those parts that when designed were never thought they would be still in use some 50 years later.
Yes, they are problematic. They do crack and often completely fail. I have seen retainers where the contact with the spring has worn a huge groove in the retainer. This is caused by the loose fit to the spring.
We crack check these every time, but that doesn't stop fatigue failures from happening. Add to this, the high spring pressures often used. Most of the time the high installed pressures are required to dampen the harmonics caused by poor cam designs.
I'm also not fan of Titanium retainers used in street engines. These need regular attention and checking. Some are coated and have good fit to the spring, but most are un coated and have a loose fit. We made tool steel retainers in the past but have decided to redesign then to fit the new spring we are about to sell. The stock springs are a good spring made from good German steel, but sometimes you need different rates and distances when using other than stock cam lift.
