Valve springs, when should you upgrade to heavier springs?
 

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.

SmileWavy

I use 993 springs in my current 964 based track engine.

In the race engine I am building -- I am moving to EBS racing springs.

I have a fabcar shifter that I added a spring to cock the throw to the right.
This requires me to pull the shifter left to downshift. For me this is a little safeguard during
shifting that the accident is a missed shift going to a higher gear, and not the other way around.

ymmv,

Mike

7K RPM. Continued operation at 7k or above requires better valve springs.

There are many choices and some of them are pretty stiff, resulting in higher rates of wear on intermediate shaft gears, chains, sprockets, idlers, cams & rocker arms.

One can easily see the consequences of using (too) stiff valve springs so such decisions should be taken very seriously.