The 1500cc exhaust manifold is a completely different casting from either 1275cc manifold, designed for the Triumph engine’s port layout, stud pattern, and physical dimensions. It connects to the head via studs with an inner and outer clamping arrangement using brass nuts and special long nuts at specific positions. The manifold-to-downpipe connection uses a gasket rather than the bell or olive arrangements found on the 1275cc.
System Specification
The gasket joint must be clean and flat for a reliable seal. If the manifold flange face shows signs of heat distortion or scoring, it should be lapped flat on a surface plate with fine abrasive paper before refitting, a warped flange will blow the gasket within a few hundred miles, producing an exhaust leak that manifests as a ticking sound from the engine bay under load.
Manifold Gasket and Studs
Brass nuts should always be used on the manifold studs, and anti-seize compound applied to the threads. The combined inlet and exhaust manifold gasket seals both manifolds to the head simultaneously, the gasket must be correctly oriented with the water passage holes aligned before the studs are engaged.