[alfa] Studs in aluminium

["John Fielding" <johnf@xxxxxxxxxxxxxxx>]

Hi All,

Studs designed to screw into ali are normally a coarser pitch than normal.  If
you look at the manifold studs the end that takes the nut is metric fine, the
end that fits into the head is metric coarse.  Ali because it has a lower
tensile strength than steel requires more thread area to get a good "bite".
When fitting a stud make sure it is absolutely clean, both the stud and the
tapped hole.  Apply a little Copper-Slip paste to lubricate the threads or if
you prefer a little Loctite for extra security.  Avoid the use of stainless
steel studs, these tend to gaul and cause the ali to pick up and clog the
roots of the stud.  Most AR heads have been helicoiled because of stripped
threads by over enthusiastic application of torque.  Of course a good torque
wrench should be used, regularly calibrated and kept in a box when not in use.
Torque wrench figures assume a wet thread, a dry thread will require
considerably more torque and this in part is the cause of stripping.

Wurth sells a huge variety of replacement studs for all sorts of
applications.

When fitting manifold studs one should not fully bottom the stud into the
head.  Screw it in by hand until the plain part meets the top of the hole then
double nut and turn it one half turn more, if it does not screw in easily then
it needs more cleaning.  When the manifold nut is fitted the stud will take a
turn or more to fully bottom and then the nut will screw on to its full
travel.  The nuts Wurth sells are self locking and very good for high
temperature applications such as the exhaust manifold.

I hope this helps.

John
Durban
South Africa
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