Ferrari Mailing List: Re: Cam timing

[Hans E. Hansen (FList]

My 1st personal cam timing experience was on - of all things - a
1972 Chev Vega.  The Vega had a very large cam sprocket that
was easily removable.  It only had one cam index hole, but I figured
out how to drill some new holes progressively off a few degrees
for each one.  I thought this was pretty smart for a 16 year old.

Anyway, cam timing is a bit counter-intuitive.  I was trying to
increase top end power.  I rotated the wrong way and ended up
with a real stump puller.   Wouldn't rev to 4000rpm

I left it that way because it would do some real righteous
burn outs.

Hans.

>
> An issue we haven't discussed at all but is important, is that the factory
> marks that happen to be there, if any factory marks are present, are a
> best-case 'recommendation'.  Like everything else in an engine, valve timing
> is a compromise.  To make a car perform at its maximum potential at 7000rpm
> means that you probably couldn't get it to idle below 2000 rpm!  This is why
> they invented the word "drivability".  And of course, that's why the most
> modern cars have variable cam timing.   My '98 M-B SL500 had variable
> exhaust cams but they just had two end-member states, switching over at
> about 4400rpm - and you could feel it switch.  My new C300 has continuously
> variable intake and exhaust cams and modulates valve timing continuously.
> That way the car takes advantage of the fluid (charge and exhaust) dynamics
> at all engine speeds and all loads - while honoring the limits of fuel
> economy and emissions (read: still a compromise).
>
> So this all begs the question; What is the right cam timing for your 308?
> The answer is going to be in the definition of "right".  Do you want it set
> the way Enzo put it, for the market to which it was delivered?  Or do you
> want it to be smoothly drivable?  Or do you want a top-end screamer with
> drivability-be-damned?  Or perhaps do you just want to pass the emissions
> tests?  Each definition of "right" will have a different valve timing
> solution.  And each setting is a compromise.
>
> Sorry for preaching to the choir but sometime folks (including me) get out
> in the weeds and forget the fundamentals - not that any of us would do that.
>
> Woohoo,
>
> rick