What do racing camshafts do

At the most basic level, camshafts are cylindrical rods of metal in piston engines with lobes protruding from them. The amount, length of time, and point at which the cams open the valves all play a big part in dictating how much power and torque an engine develops, where in the rev range it does this, and if the engine will even run at all.

As you can imagine, with the right changes a camshaft swap can seriously improve performance. However, a mistake can have disastrous consequences, not just for performance, but for reliability too. You need to be sure it will improve your car before you do so, as we have seen some swaps that have dropped huge amounts of power.

The thing with camshafts is they generally remove performance from somewhere in the rev range to add it in another, and once you add forced induction to the mix things can get even more complex. The vast majority of modern engines have four valves per cylinder, and these generally have separate cams for the inlet and exhaust valves.

So twin cams on straight engines, and quad cams on V and flat engines. Many older engines have two valves per cylinder and a single cam operating them all.

As with any moving component, things can go awry. The lobes on the camshaft can wear over time and if the system around the camshaft is not maintained well — if oil leaks from the system, or dirt and debris gets inside — then damage can occur. Problems can manifest as popping noises from the tailpipe or a ticking noise from the camshaft location,. Another problem may come from the camshaft sensor.

The system uses this data to assist in the control of the fuel injection and ignition system. If the belt snaps, the cam stops turning and the engine quits. To minimize the risk of such damage, most vehicle manufacturers recommend replacing OHC timing belts at specific mileage intervals for preventive maintenance. On older OHC engines, 60, miles is the typical replacement interval. On newer OHC engines, it is , miles.

Cam failures can occur if there are lubrication problems in the engine. Lifters create a lot of pressure and friction on the cam lobes, so the lobes and cam bearings must receive lots of oil. If oil pressure is low or the oil is dirty, the cam may suffer accelerated lobe wear and ultimately lobe failure resulting in a dead cylinder no valve action.

This type of cam damage can also be caused by using the wrong viscosity motor oil. In overhead cam engines, it is a long way from the oil pump to the top of the cylinder head. On cold mornings when the oil is thick, it can take quite a few seconds for adequate oil pressure to reach the cam. That is why most vehicle manufacturers recommend using 5W oil rather than 10W or 10W for cold weather driving.

Cam breakage or seizure is another problem that can occur in OHC engines. The cause may be inadequate lubrication but in many instances it is caused by head warpage.

When an OHC engine gets too hot, the cylinder head tends to swell and bulge up in the middle. This changes the alignment of the cam bores in the head which may cause the cam to bend, bind, seize or break.

Camshafts are often replaced to increased engine power and performance. But choosing an aftermarket performance cam is not as simple as it sounds. A lot of things must be taken into account to find the "right" replacement cam. These include not only the engine and vehicle application, but also the engine's compression ratio, type of fuel delivery system, other modifications intake and exhaust manifolds, exhaust system, etc. But most important of all, what exactly do you want from an aftermarket performance replacement cam?

More power? More torque for towing? Better mileage? As you look through the various performance camshaft manufacturer catalogs, you will notice two things.

The first is that there are many, many different cam grinds from which to choose. The more popular the engine application small block Chevy, for example , the greater the selection of cams that are offered. The other thing is that there are specific recommendations for each type of cam. So the best advice here is to follow the camshaft supplier's advice. A typical stock replacement cam either a new cam or a reground, is essentially a duplicate of the OEM grind.

This type of cam is used to restore the original performance of the engine, and is a safe choice for a stock rebuild. The next step up are the cams with slightly "enhanced" profiles. Idle quality, driveability and emissions remain about the same as stock but the engine puts out more power and gets somewhat better fuel economy. Once you get beyond stock replacement cams, the selection process gets more complicated because each grind is designed for a specific type of application.

Vehicle weight, drive gear ratios and type of transmission automatic versus manual take on greater significance as do the modifications to the engine itself compression, displacement, carburetion, valve size, valve train, etc. The most common mistake to avoid when choosing a cam is to "over-cam" an engine.

Installing a hot cam in an otherwise stock engine can create a bad mismatch between components, and that hurts rather than helps performance. A long duration cam with a lumpy idle may sound really hot, but may not provide as much low end punch as a stock cam. With more duration and valve overlap you can get better volumetric efficiency. Sign up to join this community. The best answers are voted up and rise to the top.

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