Re: Header Wrapping Tape

[Scott Fisher <sefisher@domain.elided>]

In v7 #900, Graham Hilder asks, "How do you use this exhaust tape
stuff..... one layer, several layers, big overlap, small overlap???   Or
is it simply the case that the more you layer it on, the better the
insulating effect?"

The tape I used was about 3 or 4 mm thick and a good 30mm wide, and
woven of a very thick yarn; I've since seen finer (that is, thinner,
narrower, and of a tighter weave) tape on other cars.  Given my finances
at the time, I'm sure I used the cheapest tape. :-)

Since the tape was so thick, we used one layer and minimal overlap; a
really first-rate installation should probably overlap the tape by 50%
so that each new layer lines up nicely against the bump from the
previous, if that makes sense.

We used hose clamps at each end to finish it off so that it wouldn't
unravel on track, which is something I'd seen on other cars.  Nylon tie
wraps are, of course, right out...

Ah, right -- the other justification on the M.G. was, of course, that
the carbs are right over the header on that car, so any reduction in
heat not only buys you a (theoretical) improvement in air density, but
it also avoids vapor lock or boiling the float bowls dry.  Not a problem
in an Alfa, with the exhaust and the induction separated by about a foot
of engine.  So it seems that insulating the pipe where it goes past the
brake caliper would be a good idea.  The tape is certainly light, and a
lot easier to work with than fabricating a heat shield.

One other tip: use gloves and long sleeves when installing the tape,
else the fiberglass can irritate your skin as you're constantly bending
it and wrapping it.  

And on the subject of heat shields: if the driver's compartment needs
heat shielding, I've always been impressed with the mylar bubble-wrap
stuff that a friend has used in various British vehicles known for their
ability to roast the driver -- in a street car it can go under carpeting
or interior panels, but in a racing car the application would depend on
what kind of interior trim you've left in the car.  

- --Scott Fisher

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