Tappets.

Peabody said:

I just taught the apprentice how to pack a stuffing box. I bet he's the only one in his class who even knows what a stuffing box is

In reply to ShawnG :

In his first year we spent a Sunday morning on journal bearings. As I explained how to prepare to pour babbitt, I showed him how you must first smoke the shaft

In reply to Peabody :

I regret that I have but one up vote to give.

In reply to Streetwiseguy :

20 years old and yes, But Not until I owned a motor with flat tappets.

I grew up in a time when OHV was really the only option.  I can't even remember how many tappets I've installed, rebuilt, or turned into some welded paperweight for a Christmas gift.