SBC Modified Header 1-5/8in 604 Crate

The SBC Modified Header 1-5/8in 604 Crate is purpose-built for dirt modified racing and street performance applications where maximum flow and durability are non-negotiable. Engineered for Small Block Chevy engines, this header pair delivers the exhaust scavenging efficiency that modified racing demands, whether you're competing in IMCA or UMP classes or building a high-output street machine. The 604 crate designation indicates compatibility with sealed-block crate engines, making this header an ideal choice for racers and enthusiasts standardizing their powerplants across multiple vehicles.

Constructed from heavy-gauge steel and finished in durable black paint, each header features 1-5/8-inch primary tubes that optimize the scavenging cycle for the 604's typical displacement and rpm range, tapering into a 2.75-inch collector for smooth secondary pipe integration. The stepped primary design—ranging from 1.625 to 1.75 inches—accounts for cylinder variation inherent in crate engines and improves volumetric efficiency across the operating band. This pair arrives complete with gaskets and mounting hardware, ensuring a straightforward installation without hidden costs or delays; the 34-pound weight reflects the robust construction necessary to withstand repeated thermal cycling and vibration in competitive environments.

Dirt modified racers, crate-class competitors, and performance enthusiasts benefit most from this header's application-specific engineering, particularly those running sealed 604 blocks in IMCA or UMP competition where rule compliance and reliability are paramount. Installation fits standard Small Block Chevy engine bays with minimal modification; verify collector clearance and secondary pipe routing before final fitment. The included gaskets seal against standard SBC cylinder heads, making this header compatible with both OEM and modern aftermarket heads rated for modified racing duty. For buyers seeking consistent exhaust scavenging and proven dirt-track performance in a compact, race-proven package, this header delivers measurable gains in mid-range torque and top-end power delivery.