While overhauling the mechanical systems of a classic car, it would be easy to overlook the exhaust system, even though it plays a significant role when the car does become roadworthy.

Any money invested in renewing an exhaust system will be well spent. It will increase the engine's performance, enhance fuel economy, and make the vehicle much more environmentally friendly.

An exhaust system comprises several major components, each of them performing an important role.

An exhaust system that does function to its maximum capacity does not only affect efficiency but in a lot of cases can represent a danger to the driver and passengers by allowing the excess poisonous gases generated by a car engine to not escape safely through the exhaust tailpipe, instead of pipe them into the vehicle, with potentially fatal effect.

A typical exhaust system comprises four major components, each performing a major function. The first of them is the Exhaust Manifold, where all of the waste products generated by the combustion system accumulate. These are fumes, heat, and sound.

All three of these hazards will be reduced with a properly functioning exhaust system, allowing the engine to runs smoothly, quietly, and free of all noxious odours.

When they first enter the exhaust manifold, all of the emissions are in their most volatile state. 

When renewing an existing exhaust system, signs to look for are increased engine noise, extreme vibrations in the driver’s seat, gas pedal, or steering wheel or decreased fuel efficiency.

 A damaged exhaust manifold is a condition that cannot be tolerated as it will inevitably mean that toxic fumes will begin to leak into the vehicle.

The good news is that no special skills are required to repair cracks in an exhaust manifold—just access to a suitable welding torch.

If the damage is too far advanced to be repaired, replacing the manifold is the only option- a procedure that is neither overly expensive nor too complicated.

Another source of toxic fumes generated by the internal combustion engine is the impressively named catalytic converter.

The role of the catalytic converter is to reduce the level of pollutants generated by the engine from entering into the body of the car.  These pollutants include carbon monoxide, nitrous oxide, and hydrocarbons, all of which can cause severe illness or even death.

Pollutants are directed through the catalytic converter, where they are restructured into either water and carbon dioxide.

Catalytic converters are as well known for their reliability as their longevity, meaning that if the restorer gets lucky, they may need not get involved in the tremendous costs of replacing or repairing the part. 

Because the converter comprises a block of ceramic plating, which over time can erode and crumble.

During a test drive, it is rapidly possible to detect that all is not well with the catalytic converter. It will emit a horribly intrusive noise, similar to loud rocks vibrating violently within a tin can. This is a sign that the ceramic coating is breaking up and pretty soon will begin to block up the exhaust system.

The next component to come under scrutiny should be the muffler.

The role of the muffler is to reduce the levels of noise produced by the engine so that it remains below the nuisance level.

The muffler’s official title is “ resonance dampener”. In simple terms, the muffler forces sound waves generated by the engine to cancel each other out.

If the exhaust muffler suffers any kind of damage, it will be felt instantaneously, with noise levels rising dramatically, even more so when the vehicle is being driven at high speed or undergoes rapid acceleration.

The final major component in a typical exhaust system is the tailpipe, a  long metal tube that will guide the engine’s emissions along the exhaust system and its various stages and out of the car.

The weakest links in any exhaust system are the joints and connectors that attach the exhaust pipe to each of the components in the exhaust system. These joints are particularly susceptible to corrosion, and if and when they do can cause a major failure in the exhaust system.

Generally, corroded joints are easily replaceable, as long as they are dealt with before they become too much of a problem. Remember, any flaws or defects in an exhaust system could lead to fumes venting into the vehicle.

If there are any fears that fumes are leaking, chances should not be taken, and the car shoud be taken for vetting by a professional without any time being wasted.