Date: Wed, 20 Jun 2007 01:38:28 -0500
Reply-To: Matt Roberds <mattroberds@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Matt Roberds <mattroberds@COX.NET>
Subject: Re: Loose exhaust bolt again. fix if stripped?
In-Reply-To: <20070620040727.ZQWN3928.eastrmmtai114.cox.net@eastrmimpi03.cox.net>
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
> From: Jonce Fancher <streetbugs@WHISPLLC.COM>
> Date: Tue, 19 Jun 2007 20:29:31 -0400
>
> Well the No.3 exhaust bolts seem to not want to stay tight. Is there
> a Lock tite to work in this heat?
I don't think there is, but there are a couple of options...
1) A "locking" Helicoil. Helicoil calls them a "screw-lock insert".
It's like a regular Helicoil, except one of the wire coils has
straight sections in it to provide extra pressure on the bolt.
It installs the same way as a regular Helicoil.
http://www.emhart.com/products/helicoil/standard.asp
2) A "Belleville washer" or "disc spring". This is a conical washer
that goes under the bolt head and develops quite a lot of pressure
on the bolt head when compressed. I salvaged some goodies out of a
machine at work that used these extensively, and they did a good job
of holding the bolts in.
http://www.bellevillesprings.com/serrated-safety-washers.html
http://www.bellevillesprings.com/disc-springs.html
http://www.bellevillesprings.com/belleville-washers.html
In this direction, a good (IMHO) book for answering fastener questions
in general is "Carroll Smith's Nuts, Bolts, Fasteners, and Plumbing
Handbook", ISBN 0-87938-406-9. This is an updated version of some of
the material in Smith's earlier "Engineer to Win"; he wrote a few other
"...to Win" books and the nuts and bolts one is sometimes informally
called "Screw to Win". Anyway, the book has lots of details and
practical advice for selecting and installing fasteners on cars.
(Smith worked as a race car engineer for Carroll Shelby, among other
people.)
Another suggestion, based on your idea that the bolt may be too short:
it might be good to add some really long bolts of the common diameters
and thread pitches to your bolt stash. You only really need one in each
size. The idea is to use the really long bolt as a depth gauge to figure
out the length you actually need. Also, the long bolt will do minor
cleanup on female threads, without taking off a lot of metal like a tap
can. The long bolt can also be used as a diameter and pitch gauge as
well when you've lost the bolts to something.
The "official" tool for this is a caliper with a depth gauge on it -
see the skinny part sticking out of the tail of
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47257 .
A $16 caliper is not going to reliably tell you whether something is
0.100" thick instead of 0.101" thick, but it will most certainly tell
you that you need a 30 mm bolt instead of a 35 mm one, or that it's an
M8 instead of an M6 bolt, and similar. If your tool box is full of
Snap-On or equal, buy a caliper from somebody like Starrett or
Mitutoyo; they cost more but really will find 0.001" differences and
will last longer to boot.
Standard disclaimers apply; I don't get money or other considerations
from any companies mentioned.
Matt Roberds
