Well come on now Dennis, tell them why. :-)
Dennis' aluminum flywheel was on old style flywheel that had a solid aluminum
hub. The crank bolt holes on most new aluminum flywheels are sleeved with
thick-walled steel sleeves to prevent exactly what was starting to happen to
Dennis'. The washers on the crank bolts start to bed themselves into the
aluminum of the hub of the flywheel. This results in a reduction in clamping
force between the flywheel and the crank and allows the flywheel to start moving
a little bit on the crank. The first signs are pockets around the washers and
chatter marks in the register where the crank boss sits. This is a synergistic
situation where the more it moves the more it can move, and usually goes from
barely noticeable to total failure pretty quickly. Dennis' was just showing the
first faint signs of this and I told him to swap it out for an iron flywheel
before it failed and took out other components along with perhaps his feet.... I
have seen this happen several times and it is always ugly. You can address this
by using a solid disk of steel with bolt holes in a circle that match the crank
bolt holes (in 510s and Zs you can get just this sort of piece from and
automatic car but with a Roadster you'd probably have to make it) and using this
instead of individual washers on each crank bolt. Or you can do what Tilton and
others have done and put thick-walled steel sleeves in the bolt holes. But for
the street a lightened iron (if done right) or steel flywheel is probably still
better. The clutch bolt holes are also weaker in an aluminum flywheel and there
is an increased possibility of failure there too. On a race car, that is torn
down every few races or at least once a race season (i.e. no more than say every
10 to 15 hours) this is not a problem as the flywheel can be regularly inspected
and bolts retorqued if needed. But in a street car where you expect to go
hundred of hours or more between inspections, it is just not the best material.
Some have gotten away with it, others haven't. I'd just rather be a bit more
sure about the flywheel's longevity on my street ride.
Dennis Currington wrote:
>
> I heard that some of "you" guys drive your cars pretty hard. Now me, I
> have been running an alum. flywheel for 7-8 yrs and never noticed a problem
> with street driving. Recently, during a tranny change, Mr, Sayer convinced
> me to go back to a stock one. The jury's still out on that one.....
>
> Dennis
--
Marc Sayer
82 280ZXT
71 510 2.5 Trans Am vintage racer
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