[Mark Henry]

The thread below started me thinking about when you should upgrade to heavier springs.
http://forums.pelicanparts.com/911-engine-rebuilding-forum/927266-valve-springs-upgrade-worthwhile-3-0-sc.html

I'm in agreement that a stock engine only needs stock springs, but in the thread it may leave some thinking you need the heavy springs for racing only.
Many have mild to very hot street engines with aggressive cams, twin plug, turbo, run higher RPM, rev faster, etc.
My origins is from the VW world and anything over the stock cam I would run HD springs, but I also know that a pushrod valve train is a different animal from the overhead cam the six uses.

At what point do you start worrying about valve float?
Pros and cons of running heavier springs and while we are on the subject what spring combo's have you used.