The original-equipment mild steel exhaust system replicates the specification fitted at the factory, using the same materials, dimensions, and mounting points as the original installation. For owners maintaining a concours-standard restoration or simply requiring a like-for-like replacement without the visual difference of a stainless system's mirror-finish silencer, mild steel provides the correct appearance and fitment.
TD System Specification
The TD exhaust system uses a three-stud flange connection between the manifold and the front pipe with brass nuts to resist seizure. In original form, the TD had three bolts at the front-pipe-to-silencer joint, a connection method that differed from the two-bolt arrangement of the earlier TC. The system is suspended from a front clamp and bracket at the gearbox casing and two rubber mounting kits at the rear, secured to the chassis rails. The front pipe passes through a clamp with a spacer at the gearbox bracket.
The modern replacement system uses clamp connections at both the front-pipe-to-silencer and silencer-to-tail-pipe joints regardless of original fitment.
TF System Specification
The TF exhaust system differs from the TD in two respects: the front-pipe-to-silencer connection uses a push-fit joint secured by a clamp rather than the TD's bolted arrangement, and the tail pipe is of larger diameter than the TD specification. These differences mean the two systems are not interchangeable from the front pipe rearward, even though the manifold and the manifold-to-downpipe gasket are shared between both models. The TF uses the same front bracket and rear rubber mounting arrangement as the TD.
Mounting Hardware
The system mounting hardware is common across both TD and TF. The front bracket bolts to the gearbox casing with two bolts, and a single clamp with a spacer grips the front pipe against the bracket. At the rear, two rubber mounting kits suspend the system from the chassis rails, each comprising a rubber mounting, a pinch bolt, plain and spring washers, and a nut. Four bolts secure the rear mountings to the chassis.
A replacement system includes the mounting kits and clamps as part of the complete package, and these components are also available individually when only the mountings or clamps need renewal.
Mild Steel Service Life
Mild steel exhaust systems have a finite service life determined primarily by internal corrosion rather than external deterioration. The condensation that forms inside the system during each heating and cooling cycle, as exhaust gases cool and the moisture they contain condenses on the pipe walls, is the principal destructive agent. On a TD or TF in regular year-round use, where the system reaches full operating temperature on most journeys and evaporates most of this condensation, an exhaust will typically last several years. On a car used only for short runs or stored for extended periods, the condensation accumulates without evaporating, and the system corrodes from the inside considerably faster.
Cars stored in damp environments are the most vulnerable. For owners seeking to eliminate this replacement cycle, the stainless steel alternative provides a permanent solution that is covered under Stainless Steel Exhaust Systems.
Ordering Considerations
When ordering an OE mild steel replacement, identify the model (TD or TF) as the complete system from the front pipe rearward is model-specific. The manifold-to-downpipe gasket is common and should be ordered alongside the system if the manifold joint is being disturbed. Mounting kits, clamps, and fixings are common between both models and can be ordered as needed without model-specific reference.