304SS vs. 321SS

304SS is the industry standard, and what you see the vast majority of schedule pipe manifolds constructed out of. It gets the job done, and requires piping with a thicker wall to be utilized to provide optimal strength and longevity.

321SS is a superior alloy when compared to 304SS - it has a higher nickel content and titanium added to its alloy structure to make it much more corrosion resistant, as well as less susceptible to failures due to thermal fatigue. With it being a superior alloy, we are able to construct the manifold out of thinner walled material, providing a manifold that is lighter and offers better acoustics (thinner wall/less absorption of sound waves = a racier, raspier exhaust note) without sacrifices in strength or longevity.

As of January 2023, BP Autosports no longer offers exhaust manifolds in schedule 10 304SS, but rather schedule 5 321SS. The move to S5 321SS was decided to provide BPA customers with parts crafted from a superior alloy, as well as reduce the wear and tear on both tooling and my body.

View the slideshow below for a breakdown of the aesthetic differences between the two materials. 321SS first, 304SS second for their respective depictions should the captions on each photo not be visible.

321SS Butt Weld

A series of butt welds on 321SS. Notice the pastel colors, and how the beads appear to be “wet”, or shiny.

304SS Butt Weld

A series of 304SS butt welds. Notice how the beads are duller than their 321SS counterparts, and more pink/salmon colors are present.

321SS Collector Weld

A 321SS collector weld on a 3-1 merge collector. Like the 321SS butt weld, the 321SS collector weld presents a pastel color palate, and very shiny weld aesthetics.

304SS Collector Weld

A 304SS weld on a 3-1 merge collector. Compared to the 321SS collector weld, the 304SS collector weld provides more striking, vibrant colors, and a wider variety to its color palate.

321SS Weld Penetration

Penetration on a pair of 321SS butt welds. Notice the defined ripple pattern visible on the penetration side of these 321SS welds. These welds are fully penetrated, and as strong as I can make them.

304SS Weld Penetration

Penetration on a pair of 304SS butt welds. Like the 321SS butt welds pictured last, we see a defined ripple pattern on these 304SS butt welds, as well as a more golden color. These welds are fully penetrated, and as strong as I can make them.

304SS vs. 321SS

304SS is the industry standard, and what you see the vast majority of schedule pipe manifolds constructed out of. It gets the job done, and requires piping with a thicker wall to be utilized to provide optimal strength and longevity.

As of January 2023, BP Autosports no longer offers exhaust manifolds in schedule 10 304SS, but rather schedule 5 321SS. The move to S5 321SS was decided to provide BPA customers with parts crafted from a superior alloy, as well as reduce the wear and tear on both tooling and my body.

View the slideshow below for a breakdown of the aesthetic differences between the two materials. 321SS first, 304SS second for their respective depictions should the captions on each photo not be visible.

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