[Scirocco-l] Re: Was: Stretch bolts vs. studs... Valve springs

[jdbubb@ix.netcom.com (Dan Bubb)]

rocco16v wrote:
> 
> Steve-
>   1. If you are going to run a STOCK exhaust cam on the intake (???), then
> run STOCK springs.

I think it's fairly commonly known that the 16V exhaust cam is quite a
bit more aggressive than the intake cam (20 deg more duration and .050"
more lift) and if you're up for the machining required to convert it for
intake use it will increase both the max power of the engine and the RPM
at which it happens.
Personally, I'm not sure why the stock springs properly shimmed wouldn't
be adequate for street use. They'll handle at least .423 lift and they
are the same springs that can control a 40mm intake at 7000 RPM in an
8V! Since the 16V valves are smaller and lighter they should have a
higher valve float speed UNLESS the 16V cams have higher accelerations.
I've never seen camshaft acceleration fiqures which is one of the
primary factors to determine valve spring rate, but I'd be willing to
bet they'd be comparable between the 8V and 16V. 

> 2. If you accidentally over-rev the engine, then heavier springs may save
> your bacon.  But, INTENTIONALLY over-revving is counterproductive to going
> fast.  Each engine has a point at which more revs equal LESS horsepower.
> For a stock 16V Scirocco, that point is 5800 rpm.

With an exhaust cam machined for intake use the max power speed will
increase. It will probably be a waste of time to rev to 8000 RPM unless
the engine is pretty radical, but revving into the 7's will probably be
required for max acceleration with the engine Steve appears to be
building.
Dan