CAMSHAFTS

What is a performance camshaft?

Performance camshafts are tuned for maximum performance by timing valves differently from standart camshafts.

How does a camshaft work?

The main reason the performance camshafts give power is that the valve timings are changed for performance. Here are a few things that you need to know about camshaft specifications...

LIFT: This can be cam lift or valve lift. The latter being the cam lift multiplied by the rocker ratio.
DURATION: This is the number of crankshaft degrees that the valve is off its seat.
OVERLAP: The number of degrees crankshaft that the inlet and exhaust are open at the same time.
POWER BAND: The power band on that the cam gives it maximum performance.

Lets look at this example to understand the topic better..

Piper Cams BP270 camshaft for Ford Escort 1.8 16V Zetec:

How much power gives a performance camshaft?

Camshafts for street cars can give from 10bhp up to 25 bhp according to the users needs and camshafts for racing cars can provide over 80-100bhp more.
To get more specific information about camshafts you may continue with our camshaft suppliers pages below...

Which things effect a cam's performance?

Duration: Duration is the angle in crankshaft degrees that the valve stays off its seat during the lifting cycle of the cam lobe.
Increasing duration keeps the valve open longer, and can increase high-rpm power. Doing so increases the RPM range that the engine produces power. Increasing duration without a change in lobe separation angle will result in increased valve overlap.

Overlap: Overlap is the angle in crankshaft degrees that both the intake and exhaust valves are open. This occurs at the end of the exhaust stroke and the beginning of the intake stroke. Increasing lift duration and/or decreasing lobe separation increases overlap.
At high engine speeds, overlap allows the rush of exhaust gasses out the exhaust valve to help pull the fresh air/fuel mixture into the cylinder through the intake valve. Increased engine speed enhances the effect. Increasing overlap increases top-end power and reduces low-speed power and idle quality.

Lift: Lift refers to maximum valve lift. This is how much the valve is "lifted" off its seat at the cam lobe's highest point.
The intake and exhaust valves need to open to let air/fuel in and exhaust out of the cylinders. Generally, opening the valves quicker and further will increase engine output. Increasing valve lift, without increasing duration, can yield more power without much change to the nature of the power curve. However, an increase in valve lift almost always is accompanied by an increase in duration. This is because ramps are limited in their shape which is directly related to the type of lifters being used, such as flat or roller.

Timing: As we think of an example 22-62, 62-22;
The first 22 shows how many degrees the inlet valve opens before top dead center,
The first 62 shows how many degrees the inlet valve closes after bottom dead center,
The second 62 shows how many degrees the exhaust valve opens before bottom dead center,
The second 22 shows how many degrees the exhaust valve closes after top dead center.
Duration and Overlap is calculated by using these values.

Points to take precaution: Allthough fast road camshafts can be used without making any modifications on the engine, the top level camshafts (Road Rally or Race), which have long duration and more lift need some precautions to install.
Because performance camshafts increase the power and also the power band, the engine would rev more than before with a performance camshaft. As a result of Duration and Lift are also longer and higher than before; at high revs, the piston and valves may become closer to each other. In this case, it's very risky to occur a position like they crash to each other. To avoid such a situation, the camshaft producers provide special valve springs. These springs are both tenser and lighter. That helps the valves to take their position in valve seats just in time, so unneeded damages are completely prevented in this way.
Valve spring replacement is an extra-important point to take care about top level camshaft installations.