A polished heatshield replaces the original painted pressed-steel item fitted between the exhaust manifold hot-spot area and the carburettors. The mirror-polished stainless steel finish reflects radiant heat more effectively than the original painted surface, keeping the carburettor float chambers cooler during prolonged driving, reducing the risk of fuel vaporisation in the float chambers that causes rough running, hesitation, and hot-start difficulties on the C-series engine. The polished finish also provides a striking engine bay detail that complements chromed air filters and polished rocker cover fittings. The heatshield fits in the same position as the original using the existing mounting points, with six screws, spring washers, and plain washers.
The Heat Soak Problem
Heat soak is a particular issue on the C-series engine because the exhaust manifold and the inlet manifold with its carburettors are on the same side of the engine, in close proximity. The hot-spot connector, which deliberately transfers exhaust heat to the inlet manifold to aid fuel vaporisation during warm-up, also transfers heat to the carburettor bodies and float chambers after the engine has reached operating temperature. When the car is switched off after a run, the under-bonnet temperature rises sharply as airflow ceases while the engine and manifolds continue to radiate heat. This heat soak can raise the float chamber temperature enough to vaporise the fuel sitting in the jets and chambers, making the engine difficult to restart.
The polished heatshield's superior reflective properties reduce the radiant heat reaching the carburettors both during running and during the critical heat soak period after the engine is switched off.
Fitting
The heatshield is a straightforward fitment using the existing mounting points. The six screws with spring washers and plain washers should be tightened evenly to hold the shield firmly in place without distorting the polished surface.
The original painted heatshield can be retained as a spare, it remains perfectly functional and can be refitted at any time if the owner wishes to return the engine bay to standard appearance for concours judging.