Stebro

[Larry C Leung]

Tess,

In water cooled cars, the main reason that the exhaust is wetter than in
air cooled is that the exhausts are generally longer and further from the
engine, thus making it cooler, as you pointed out. The type of cooling
doesn't matter, all else being equal. 

The reason for using SS for either engine is precisely for it's
resistance to corrosion (if it's truely stainless). Though it may not
hold up to the heat of headers as well as say ceramic coated steel
(though some grades of SS are, when I used to work in the nuclear reactor
industry, anything we made that went into the reactor core was always
made of SS (don't recall the grades) which reaches temps far in excess of
an exhaust header in a water cooled car (probably comparable to air
cooled, which gets some of their cooling from the exhaust, hence the
heater boxes), the beauty of SS is it's corrosion resistance in hostile
environments. Witness 100/200 and A series exhausts (my 12 yr old 200's
is fine) and even the lowly Ford Taurus (my folks is 14 yrs old, and it
hardly sees highway temps to get it hot).  Even GM is using SS (though a
grade that will SURFACE rust, 301 me thinks) the motivation being the EPA
regulation that emissions related components last 100 k miles or 10 yrs
(and you thought that those new drivetrain warrantees were because mfg's
were hawking their own quality), so SS meets the needs perfectly (note
301 is less costly, easier to work and weld, AND magnetic, thus lending
itself to magnetic sorting tooling). Note the last GM air cooled product
bit the dust around 1968 or so. 

In summary, for a street car, SS makes sense for a long term vehicle. As
I joined this thread late, as pointed out earlier, the reasons racers use
steel is different, the key being racing cars aren't intended for the
long term. For street cars, as long as I can afford it, I will use SS on
a street car, though I'd have to admit, my Solo2 GTi has a coated mild
steel Gillette exhaust, which is, by the way, losing the battle to the
tin worm compared to my 200's SS exhaust, and it's newer (installed new
in '92).

Hope that clears things up a little,

LL - NY (the (road) rust belt)