What are Vernier Camshaft Timing Pulleys

[thexav]

Do Vernier Camshaft Timing Pulleys have any performance benefits on a standard engine?

What makes these different to standard camshaft pulleys?

 

[SLEEPER]

They give better adjustment but it is only likely to benefit tuned engines

 

[obi_waynne]

Cams are aligned on the teeth of the cogs, these allow adjustment to fractions of a tooth. It is very precise and as @SLEEPER says they have a place on highly tuned engines.

The outer ring can be loosened up and rotated slightly allowing earlier or later cam duration times.

 

[old-git]

Before vernier, there were offset dowels. My Twin Cam engine used these. They allowed similar fine adustment like verniers, but with a lot more hassle. With the huge valves I was running, offset dowels allowed them to miss each other by 10 thou. Somewhat marginal but the power was worth the risk