The Carburettor is the default air to fuel mixing device on all cars prior to the introduction of Electronic Fuel Injection in the early 1980's. It's job is to mix the correct air to fuel mixture and stop the engine running lean or rich. To add to it's job, it also needs to operate correct in the following situations, cold start, hot start, idling, part throttle and full throttle. The carburetor is basically a long tube which narrows in the middle and then widens again, creating a venturi effect in the middle which speeds up the airflow and creates a vacuum effect. At this narrow section there are holes/jets located where fuel is sucked into the airflow because of the venturi effect, creating the combustion mixture. The airflow is controlled by a throttle valve (butterfly valve) located at the venturi section, this valve carefully control the flow of air as required normally controlled via a cable attached to the accelerator petal. It can alter the amount of airflow, which in turn alters the amount of fuel delivered which equals more power. It is possible to fit larger Carburetors also with multiple barrels and venturi, which not only can increase the engines fuelling requirements in terms of flow rates but also BHP potential. Engine compartment space will be a considerations, especially the bonnet area above the cylinder block, with some installs protruding out of the bonnet.

A critical part of the engine and are connected to the crankshaft via chains or belts (timing belt, timing chains), camshafts are driven by the camshafts and also control the valves. This relationship controls the air to fuel mixtures (traditional injection systems) and exhaust outlet via operation of the values. The Camshaft operates these valves by lobes located on the camshaft shaft themselves, as they rotate around pressing the valves downwards. The valves are spring loaded ( can be pressured air actuated) and return to the original location, waiting for the next time the lobes rotate back round, continuing the cycle. There are both air inlet and exhaust outlet valves and on some engine design like DOHC (double overhead cam) can have two sets of valves per inlet or outlet. You can imagine that the crankshaft is connected to the camshafts via the cambelt, and the camshafts are connected to the valves, all working in synergy. During normal operating conditions a standard camshaft profile could be tailored for certain engine characteristics, but there are variable value set-ups which can even changed the cam profile for performance use- Honda is especially known for such technologies.
CAMSHAFT TYPES.
SOHC (Single Overhead Camshaft):
1 Single Camshaft, with normally 1 inlet and outlet valve per cylinder. In V-type engine configuration, this will mean one cam per head.
DOHC (Double Overhead Camshaft):
2 Dual bank of camshafts, normally with 2 inlet and 2 outlet valves per cylinder. Due to the increases in inlet/outlet and valves, the engines power and efficiency is increased due to the volume increase capacity.

PUSHRODS: Exclusively found in V-type engine designs, used to actuate rocker arms to move the valves, with the camshaft located in the engine block. This system does increase the mass of the system and has limitations in RPM's (revs per minute) compared to DOHC designs.

The crankshaft (referred to as crank sometimes) is responsible for converting the explosive power generated from the combustion chamber, which is transferred through the piston and connecting rods, which in turn are connected to the crankshaft. It in turn controls the camshafts via the timing belts or chains and they control the valves and so the cycle continues. The crankshaft can be viewed as the backbone of the engine. The crankshaft is connected to a flywheel, which helps smooth out torque characteristics and this is in turn connected to the clutch. Essentially as the piston is moving up and down during the different stages of the OTTO cycle, the downward pushing forces are converted into rotational motion which can drive the wheels via the drive-line, through the flywheel. It is important when other tuning upgrades are applied to the engine increasing BHP and torque levels above standard specification, that careful consideration is taken to the crankshaft. As the additional loads and stresses can cause the crankshaft to become strained and in extreme cases break and destroy your engine.
CAST IRON CRANKSHAFTS:
Traditional crankshafts are made from cast iron, while cheaper to produce they are relatively heavy and casting will not produce as high quality as forged or billet machined pieces. They are made by pouring molten metal into a cast and the quality and strength of the piece is the lowest available.
FORGED STEEL CRANKSHAFTS:
It is possible to fit forged steel items which can be lighter in construction and stronger then cast items, also their elongation properties (ability to stretch) is increased. This makes forged items more durable to the stresses imposed on them especially in high powered horse power and increased torque engines. Forged crankshafts are made from a single piece of metal and are shaped to the desired design by the forging process, this is one of the most popular types due to their increased specification and mid-level pricing.

The cylinder head is the last air restriction going into the engine and the first restriction exhaust gases faces entering the exhaust manifold, having exited from the engine. This in turn does have an affect on your choice of induction (air filters, turbo, superchargers) and exhaust ( exhaust manifold, downpipes, cat and silencers) capabilities to increase power developed by the engine. So any money and BHP potential could be wasted on these systems if there isn't a effective cylinder head design in place. Like most other types of car upgrades and tuning available, careful set goals needs to be confirmed prior to product selection, a race cylinder head and road cylinder heads will be designed for different applications. One with outright power and BHP efficiency, while the other might have fuel economy and drivability in mind. Also the following in turn effect how well the cylinder head produces power: Ports,values, combustion chamber and the material the cylinder head is made from. A cylinder head are effectively the lungs of the engine and by increasing it's efficiency you will gain more power and torque as a result. The more fuel and air mixture in and more exhaust gas out on on each camshaft revolution, the greater the rewards. Camshafts do play a big impact on the cylinder heads capacity to yield improvements, as they ultimately control the valves which open and closes during the OTTO cycle. It is normally best to fit the biggest valves possible for maximum BHP gains and outlet valves are normally around 75% smaller then inlet valves (due to them being helped by the pumping effect of the engine). Even a engine with standard cams will yield BHP and torque improvements over the entire rev range (broader power band) with a upgraded cylinder head, also fuel economy will improve due to greater inlet and outlet flow capacities.

The Compression Ratio of the engine greatly affects it's ability to generate brake horse power and normally the higher the figure the greater the performance potential. Also there is better throttle response and increased fuel economy due to the ability to burn fuel more completely under greater engine pressures. Why not design engines with larger compression rations? Well firstly the advantages only work up until a certain level and depending on the engines design, detonation is more likely with increased levels. If we look at a naturally aspirated engine (10:1), then raising the compression ratio and using higher octane fuel conservatively will likely be fine, but careful camshaft consideration also needs to be taken into account due to intake and outlet timing associated with this. Race specification compression ratios can be between 13:1 or 15:1 levels. Generally speaking cars with forced induction will require that lower compression ratios are used, due to the increased chances of detonation under the already compressed air intake. Also the lower the compression ration the higher the boost levels can be used under the forced induction set up. Diesel engine due to their design characteristics, will come with higher compression rations then their petrol cousins. With levels in the 21:1 ration being quite normal, this also means by the very nature of their construction, internal components are generally a lot stronger in design.

The Engine displacement is the measurement of the total volume of the pistons covered by the pistons in the combustion chamber, from Top Dead Centre (TDC) to Bottom Dead Centre (BDC). Essentially the larger the displacement, the larger the air and fuel mixture capacity, with more power potential. It is possible to increase the engine displacement by boring out the cylinder block and using larger pistons, but careful considerations needs to be taken with the compression ratio, due to the increased danger of detonation.

STROKER KIT:
Essentially this is a way of increasing the engine displacement with out the need to increase the cylinder bore and pistons. This achieved by fitting the stroker kit which changes the crankshafts crank pin location, which lets the piston move further in it's vertical motions. While this does increase the overall BHP power and torque levels normally throughout the rev range, it can affect the ability of the engine higher up towards the red-line limit. This is because the crank and piston has to move faster in a rotation to cover the increased distance travelled, but with in the same time period. Also due to the increase in revolutions, piston wear will increase as a side effect. It maybe better to consider the rebore and piston change for engines operating in higher rev range.

The ECU ( electronic control unit) or computer chip as it is known, can be viewed as the electronic management system controlling the entire engines preset operating thresholds. Since the early 1980's it has now become the norm to have these devices in place and these ECU chips are capable of making thousand's of calculations per second and rely on the use of many sensors through the entire car to check and recalculate set perimeters. While great care and attention is made to make these devices fully functional and well set up from the factory, the manufacturers goals will most likely not have performance as the top of their agenda and it is possible to increase both torque and bhp with after-market or re programmable ECU chips. Factors such as high attitude, weather temperatures and climates and fuel grades- vary agross the world, so de-facto software parameters are easily upgraded to boost performance.

The pistons are driven by explosions in the combustion chamber, when the air and fuel mixture is ignited, their job is to drive the crankshaft via the connecting rods to convert the downward motion of the piston into rotating motion of the crankshaft to drive the driven wheels. These components are subjected to huge forces and there design and material construction are critical in keeping the internal workings of the engine, in high stress environments safe. As with all components in standard road cars, unless the vehicle is designed with the intention of being subjected to a high revving Motorsport race series, it is unlikely manufacturers will use the best materials and designs for performance applications.
FLAT HEAD PISTONS:
This is normally the standard for OEM specifications and is fitted from the factory in conventional combustion engines.
DOMED HEAD PISTONS:
Helps to increase the compression ration in naturally aspirated engines, to improve throttle response and fuel economy, can increase the risk of detonation.
DISHED HEAD PISTON:
Critical for forced induction applications as it helps lower the compression ration and lets you run more boost, lowers detonation possibility.

Throttle Bodies are located with in the induction system, in between the intake manifold, MAF sensor( mass air flow) and air filter. They control the air entering the cylinder head inlet valves via a butterfly valve, this is normally linked to the accelerator pedal or electronically in fly-by-wire applications. Essentially when the accelerator pedal is pressed, the valve opens up allowing more air to enter the intake manifold, the air to fuel ration reads the airflow via the MAF sensor and adjust the fuel requirements accordingly through the engine management system. There are some similarities between throttle bodies and carburettors in that they both control the airflow, minus the venturi and fuel jets. Also in terms of performance upgrades, it is possible to have multiple throttle bodies linked via chains to increase the airflow rates and it is even possible to have one throttle body per cylinder for extreme applications.

The valves are controlled by the camshaft and it's lobes, their job is to govern the inlet fuel-to-air ration and exhaust output from the combustion chamber. They are located in the cylinder head and are pressed downwards by the lobes of the camshaft and return to their resting position by springs normally. When the Cylinder is gas-flowed, it is possible to fit larger valves, which in turn increase both the volume of both air and fuel mixture and exhaust venting, from the combustion chamber. Also the materials used can be altered, for example by using forged items which will increase the strength of the items for more heavy use applications. While viewed as quite a simple piece of the engine, their roles is critical to gain more power and performance, especially when considering the result of these not working correctly.

THERMAL BARRIER/CERAMIC COATING:
Specially designed to treat components which will be subjected to huge heat exposure, this coating helps to drastically reduce these effects and further protect your investment, especially suited to cylinder heads, intake manifold, valves, pistons, headers and exhaust components. This coating can be applied to metals as well as composites and are used in F1 for example.

ANTI-OIL COATING:
This coating is applied to many internal engine components to help reduce friction of moving parts, which not only increase efficiency but power robbing drag of moving components.