Don't forget that many Spits had stock dual springs.
So fitting them is not necessarily a risky modification
(depending, of course, on how strong the new springs are).
Doug Braun
'72 Spit
At 11:06 PM 11/11/00 , you wrote:
>But wait! There's more!
>
>Dual springs also allow the designer/engineer to set the resonant
>frequency of each spring to a different value, and to get some damping
>into the system so that it can operate closer to the resonant
>frequency. The springs operate close to each other such that the
>inner spring's OD clears outer spring's ID by a small amount.
>Friction between inner and outer coils damps the resonance.
>
>And all the rest that Carter mentioned is true, too.
>Donald.
>
>
> > Date: Sat, 11 Nov 2000 17:48:35 -0800 (PST)
> > From: Carter Shore <clshore@yahoo.com>
> >
> >
> > Main advantages of dual springs:
> >
> > 1) Allow greater valve lift by reducing the bind
> > height of the coils (two skinnier springs can be
> > compressed more than one fat spring)
> > 2) Allow higher overall spring rate, to raise the RPM
> > where valve float occurs. (sum of the pressure from 2
> > skinny springs can be greater than the pressure from
> > one fat one)
> > 3) Allow longer spring life, by reducing the torsional
> > loading on the spring material.
> >
> > Skinny and fat refer to the thickness of the wire that
> > the springs are wound from.
> >
> > Unless you are running a higher than stock lift
> > camshaft, higher ratio rocker arms, reving above 7,000
> > RPM, or powering an aircraft, then dual springs will
> > be of little benefit.
> >
> > BTW, the valve seats need not suffer. It depends on
> > the spring rate and the installed height of the
> > package (springs, retainers, shims) used. Static
> > closed seat pressure does not have to be any higher
> > with duals than singles. The machine shop should check
> > this, it really is important.
> >
> > But they *do* look cool!
> >
> > Carter Shore
|