Do these help?
Some people keep the stock rockers bec they have less mass than the Yellas.
On the other hand, Yellas are supposed to have less flex than the stock ones, and they are fully rollerized. I like the idea of having less flex.
From here, there is a debate about whether the rollers actually rotate enough under engine speeds to cause less friction than the stockers, or to help realize any more horsepower than the stockers.
There are a number of threads about this if you do a search.




