4in Single Inlet Air Plenum

The 4in Single Inlet Air Plenum by SPECTRE is a precision intake manifold component engineered to optimize airflow distribution in high-performance engine builds. This plenum chamber serves as the critical transition point between your intake runner and fuel-injected engine bay, consolidating incoming air charge before directing it to individual cylinder ports. Whether you're upgrading a street machine, carbureted classic, or modern fuel-injected platform, a properly sized plenum reduces velocity losses and smooths air distribution across all cylinders for balanced combustion and improved throttle response.

SPECTRE's 4-inch single inlet design minimizes turbulence and resonance that typically occurs in undersized or poorly-shaped plenums, allowing you to maintain velocity where it matters while preventing high-frequency reversion. The single inlet configuration simplifies plumbing in tight engine compartments while the ample internal volume (6 x 4.5 x 13.5 inches) ensures adequate plenum runner length for optimal volumetric efficiency across your target RPM band. Cast or precision-fabricated construction withstands manifold heat cycles and fuel system pressures, making this component a reliable foundation for carbureted, TPI, or modern EFI fuel delivery systems seeking consistent air metering.

This plenum is ideal for small-block Chevy, Ford, and Mopar engine swaps where factory intake manifolds prove restrictive or incompatible with performance cylinder head ports. Installation requires careful port-matching to eliminate air leaks at runner junctions and proper gasket selection to ensure repeatable carburetor or throttle-body alignment. At 2.95 lbs, the compact weight reduces upper-engine mass while the 4-inch diameter inlet accepts standard 4-inch diameter air cleaner bases and velocity stacks, making integration into existing intake systems straightforward. Verify your intake runner port configuration and cylinder head casting numbers before ordering to confirm fitment compatibility with your specific engine platform.