Exhaust Manifold Header for Triumph Spitfire (1975-1980) 1.5L Engine

High-Flow Exhaust Manifold Header for 1975-1980 Triumph Spitfire (1500 / FM)

What It Does: This 4-1 tuned exhaust header replaces the restrictive factory cast-iron manifold to optimize exhaust scavenging and significantly reduce backpressure for improved throttle response.

The Stock Spitfire Weakness

The 1975-1980 US-spec Triumph Spitfire 1500 was equipped with a heavy, "log-style" cast-iron manifold that was primarily designed for emissions compliance rather than airflow efficiency. This OEM unit creates massive backpressure, trapping high-temperature gases within the cylinder head and causing significant heat soak. Over decades of thermal cycling, these cast units are notorious for developing hairline fractures and warping at the mating surface, which leads to persistent exhaust leaks and a loss of compression efficiency. Furthermore, the restrictive internal diameters of the stock manifold choke the engine's top-end potential, limiting the already modest output of the 1493cc powerplant.

The Engineering Solution

This performance header is engineered with a 4-1 long-tube design to maximize the scavenging effect, using the velocity of exiting exhaust pulses to pull remaining spent gases out of the combustion chamber. Constructed from high-grade stainless steel with a combination of TIG and MIG welded joints, the assembly offers superior corrosion resistance and weight reduction compared to the stock iron unit. The 1.20" primary inlets and 2.0" OD outlet feature mandrel-bent tubing to maintain a consistent internal diameter, preventing turbulence. CNC-machined flanges ensure a perfectly flat mating surface to eliminate leaks, while the integrated O2 sensor bung allows for seamless integration with existing setups. Expect dyno-verified gains of 5-10 HP and improved mid-range torque across the powerband.

Technical Specifications

Compatibility

• 1975-1980 Triumph Spitfire Base
• 1975-1980 Triumph Spitfire 1500 (US & UK Models)

The Triumph Standard

For the classic British roadster enthusiast, maintaining mechanical harmony is vital. This header provides the precision and increased thermal efficiency required for the 1500 engine, delivering a crisper exhaust note and more aggressive acceleration without sacrificing the vintage soul of the Spitfire. It is a bolt-on solution for those looking to modernize their engine's breathing capabilities.