The two most common types of stainless steel
used in exhaust systems are T304 and T409,
let's take a look at the differences between
the two.
Both 304 and 409 are corrosion resistant,
the difference is the amount of chromium used.
304 contains about 20% chromium whereas 409
contains about 11%.
This difference, plus the added nickel makes
304 stainless a higher grade steel, making
it more resistant to corrosion and giving
it a better finish.
You can polish 304 up to a high luster.
As you would expect, 304 stainless is more
expensive but for lasting durability and good
looks, 304 is the way to go.
For vehicles that don't see salted roads,
you can save some bucks and go with 409.
While 409 can develop surface rust and discoloration,
it won't damage the integrity of the exhaust.
When appearance is not so important, but performance
is, 409 might be a better choice.
In regards to horsepower, there are no gains
to be made between 304 and 409, they both
perform equally.
There is also no real weight advantage between
the two.
An easy way to tell them apart is with a magnet.
409 is magnetic, while 304 is not.
For maximum durability and finish, go with
a 304 exhaust system.
For warmer climates, 409 is more practical
and economical.
Be sure to check out our huge line of exhaust
systems at Holley.com
