On Wed, 24 Apr 2002, Hugh Fader wrote:
> Similar to my question on con-rod bolts: Is there anything special about TR6
> flywheel bolts?
They are nothing too special...BUT
> Can I purchase grade 8 bolts the same size to renew them?
Do no do this. If you must use alternate source bolts, chose one of the
following:
1. "Superbolts" like the ARP FBT716-4 (I think these are a special MIL
spec or NASA spec bolt) Note: these are available at www.aptfast.com for
about $14.95, but you need special washers for them which is another
$5.50 or so.I have NFI in APTFAST, they are pretty good folks in my book.
2. really, really hard bolts that are used in tooling applications.
The bolts are 7/16-20, that's no big deal, but you want the shank portion
to be appropriate to the thickness of the flywheel and the threads are
"longish" for the application. I forget the actual threaded portion
numbers.
At any rate, the big deal here is (and this is especially true for a stock
TR6 flywheel) that there's a lot of mass at the end of the crank, and as
you can imagine that mass added to normal harmonic motion of the end of
the crank puts not only shear forces on the flywheel bolts but _tension_
too. In otherwords, the flywheel tries to pry the bolt heads off.
Normal bolts will stretch a bit under this tension, and if not stretched
too much will return to their normal length. However, bolts that are too
soft will not return to their normal length and may even completely yield
to the forces involved. If you're lucky, you get a vibration from the
motor and you turn it off and call AAA (or your favorite transportation
source). If you're unlucky - consider 28 pounds spinning at 3 or 4k RPM's
and the forces that flywheel is capable of. Now, measure the location of
the flywheel to your normal feet location in the footwell and guess what -
your feet are at peril!
The stock flywheel bolts are pretty darn good, and most of the replacement
bolts that I've purchased are okay (I've gotten them from Moss or TRF).
But if you like to rev. your motor a lot and/or you want a bit more
insurance that the flywheel will stay put. I highly recommend the ARP
fasteners. They are "good stuff".
If you want more details on the bolts themselves, I can eleborate.
> Thanks,
> Hugh Fader
regards,
rml
p.s. If you want some good reading on nuts and bolts, the book "Nuts,
Bolts, Fasteners and Plumbing" by Carroll Smith is an excellent source.
He's fairly opinionated, but with good reason. Highly recommended. Oh, and
after reading Carroll, you may think twice about going to the hardware for
nuts and bolts for certain applications... don't get me wrong here, I
still buy tons of bolts from the hardware store, it's just that certain
things demand exactly the right bolts. The fhywheel attacment bolts are
one of those things.
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