Downpipes melting fans

[Peter Serwe]

What I've heard about header wrap, and haven't used in since I heard it,
was that it keeps the heat in the pipes, insulating it, if you will, keeping

your exhaust gases hotter, and keeping the heat out of your engine
compartment.  This allegedly accomplishes a few things.

First and foremost, from a performance standpoint, it's supposed
keep your exhaust gas velocity up, because the gas doesn't contract
from the temperature lost, as cold air translates into more air in, hotter
air further down the pipes is supposed to help evacuation.  I don't pretend
to understand the thermal/fluid dynamics, or whatever else is involved.

That performance gain aside, it also keeps your running hotter, which in
turn
stresses/weakens the steel, stainless gets more brittle the more you temper
it,
far as I know, mild steel does too, just not quite as bad.

Lastly, it's been stated by a bunch of ex nascar guys I know that when they
ran wrapped headers on sb chevy's, they'd just throw them out and replace
them
after every few races, or race.  So basically, if you want to replace them
all the time,
and 400 bucks a season autocrossing is okay by you just for headers as a
consumable item, then go for it.  Wrap the crap out of them, let us know
if it actually registers on the dyno :)  I know summit sells header wrap
kits in
various length/width combinations.

As always, this is IMHO, I'd love to hear anyone with more than
hearsay/layman theory to jump in and correct me, as the case
may require ;)

Matt Sfeir wrote:

>  I've heard that header wrap will cause the downpipe or whatever exhaust
> it's
> wrapped around to crack.  Any opinions?

--
Peter Serwe <peter@easytree.net>
Cheaper, Faster, Better, pick any two.
finger peter@easytree.net for public pgp key