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Metal Guru
Join Date: May 2001
Location: Beverly Hills, Michigan
Posts: 2,526
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Grade 304 austenitic stainless is not recommended for "hot service" (between the exhaust manifold and the catalyst). It is prone to corrosion cracking. It is the material that most aftermarket fabricators choose, unfortunately.
OE's use 409 (ferritic stainless) as it is not susceptible to corrosion cracking and the cost is relatively low.
Grade 321 austenitic stainless is also good in hot service but is more expensive. It is used primarily in aircraft.
Headers made from 321 stainless (like those sold by Brian) are worth the investment.
I have a header that Ben from M&K made for me 10 years ago. It's fabricated from 321, has not cracked and probably never will.
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Paul B.
'91 964 3.3 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, H&R Coilovers, ESB spring plates- 210 lb
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