Ok...I will take a shot at this.  Performance cams will generally increase
lift (amount that the valve is open) or duration (time that valve is open)
or both.  Some cams will also change the point at which the valve opens, but
this is more often done with an adjustable cam gear/sprocket.

As for why VW chose the cam that they did, the answer is simple: compromise.
The cam that they chose had to give a good idle, smooth power and torque
curves and of course pass emissions controls while still maintaining
reliability.

One thing that you may want to keep in mind is that most cams are sold "for
off road use only" but I believe there are a few that have received CARB
certification.

Oh, and FWIW, all I-4 VW 8V hydraulic lifter cams are interchangeable.

HTH,

Scott

----- Original Message -----
From: "Bill Marshall" <Willolyn99@AOL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, November 19, 2003 10:11 AM
Subject: Re: FS, some stuff :) (cams)

> OK, time to profess my ignerunce.  What does a different cam do to change
the
> performance?  I see these cam upgrades for many different vehicles, and I
> don't get it -- why didn't the VW engineers use that design in the first
place if
> it's better?
>
> Bill Marshall
> '85 GL Tiico "Pandora"
> Aurora, IL
>
>