> Scott Speirer wrote:
 > >
 > > With regard to Perry Mick's tension bolt failure, I highly doubt that
 > coating the new
 > > or original tension bolts during the rebuild is going to prevent a
 > recurrence of a
 > > failure.  You might as well cover them with bovine scatal matter before
 > installation
 > > - the amount of protection will be the same.

 > Mark Wrathall
 > RTV is probably easier to obtain in S.Cal, easier to work with and less
 > corrosive :).
 >
 > I was also suprised by this suggestion, but when you think that the RTV is
 > not changing the resonant frequency by added weight, rather is damping the
 > bolt by submersing it in a thick fluid in an enclosed space, you can see
how
 > this idea has merit. The fact that has been considered a remedy in the
 > racing scene adds at least circumstantial evidence that there is some value
 > in it. Although it is of unproven benefit, the pain/risk/cost involved in
 > doing makes it worth trying.

 I am not sure about that. We got a lot of cows out in Covina :-) Cowvina?

 When RTV sets up it is fairly high durometer. Not really a fluid.
 How do you classify rubber? Not a solid.

 Paul Lamar
   >>

Hi Paul...

I agree that RTV will change the vibration characteristics of the bolt.  I
use the RTV to seal both the split cases of our helicopter transmissions and
top and bottom of the bolts to stop oil migration.

When I was working on the GM rebuild project for 2.5 years.  We were
recycling all the hardware of the engines including head and crank bolts.
These bolts were about the same age as the 13B's and just looking at a bolt
can some times identify problems.

Cull any bolts that the threads don't look like they are evenly spaced.
Cull any bolts that don't enter the threads easily, finger pressure.

We also use a device torque to yield which had a sensor that detected when
the bolt was stretching.

Good luck.

Rick Stitt

It is possible that Perry runs full power around 5000 RPM while most
of us run full power only at 6000 RPM because of fixed pitch prop
load. That could change the forcing function to be more in the
range of the resonant frequency of the bolt. Hopefully ARP will
discover the the resonant frequency and let us know.

Paul Lamar
 
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