The exhaust manifold in your Chevrolet Corvette will most likely be constructed of cast iron or stainless steel. The job of the exhaust manifold is to collect the gases vented by your Corvette engine’s multiple cylinders, and collect it into one pipe, the exhaust pipe. A particular kind of manifold, a header (extractor in Australia), can be installed to decrease backpressure and therefore increase efficiency of combustion in your Corvette engine.
An exhaust manifold works like this. When a piston begins its exhaust
stroke, it moves up the cylinder. This movement reduces pressure in the
cylinder which helps expel the exhaust gas. This moving exhaust gas is
called an exhaust “pulse.” The gas then enters the manifold where it is
collected. The gas then flows into the exhaust pipe, through the
muffler, out past the tip and into the atmosphere.
Headers function to increase the velocity of the exiting exhaust gas.
Tuning the header is an attempt to time when each exhaust pulse occurs,
in succession, one after the other while the gas in still in the
exhaust system. The result is an increase in velocity of the exhaust
gas so that it exits quicker. This means the next pulse can enter
sooner. In V8 and V6 engines the Y- and X-pipes attempt to get the same
result. The more quickly and efficiently the exhaust gases exit the
cylinders, the more efficiently your Corvette engine operates. The
result is more efficiency, torque, and power.