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Considerations when Upgrading Camshafts

The choice of a camera can cause anyone a headache , especially in the event that they pick the wrong camera for the job. There’s an abundance of science when choosing a cam So keep reading and we’ll assist you in navigating through the finer points.

The camshaft is other than an iron or cast shaft that has a number of lobes that are strategically located across the length. Each lobe opens and shuts an air valve by moving the pushrod, lifter and rocker arm. Or in the case of an overhead cam engine, by moving a cam follower , or directly valve action.

The shape, size and position of the camshaft’s lobes determines the valve’s timing as well as the engine’s compression and breathing characteristics. This will determine the potential performance of the engine and the rpm range in which the engine can produce the most torque and power.

The selection of which “right” Camshaft thus isn’t just the foundation of an engine with performance, but its central point. The cam creates the engine and is the main factor in determining the other components to be selected to build an engine (cylinder heads pistons, valvetrain manifolds for exhaust and intake along with carburetion).

The majority of manufacturers of camshafts offer an array of off-the-shelf grindings that are specifically designed for particular applications. The key to selecting the right cam to give you the performance you require is to identify the rpm range at which the engine is expected to produce the highest power. Then, you can choose one that is compatible with the breath characteristics of the the exhaust and intake manifolds, the weight and the gearing of the vehicle that the engine will be running in.

If you are building a large stroker motor to be used in an ProStock drag car, with an aftermarket 500-600 cubic inch block, and piston heads that have fist-sized ports , which flow over 500 cubic centimeters at .900″ the valve height, this engine will require a huge cam with plenty of lift in the valve, length, and overlap.

However when you’re building a smaller street-performance block intended to be a daily driver that has auto transmissions and standard gearing, you’ll need a cam that offers decent drivability and plenty of mid- to low-range acceleration and throttle responsive. You should also select engines with tiny intake runner volumes to ensure excellent air velocity and throttle response in the low to mid-range speeds and a split-plenum 180-degree high-rise intake manifold, and a properly-sized carburetor.

Don’t overdo your work

The biggest error that engines builders commit is to overcame an engine. A cam with too much lift in the valve or duration as well as excessive overlap of valves to the purpose could result in negative effects.

Everyone likes big numbers however, if the specifications for your cam aren’t in line with the engine you’re building , or the specific application it’s being used for You’ll end up with an engine that isn’t performing well and does not exceed the expectations of your client.

Keep Your Eyes on Valve Lift

The higher the valve lift, the valve even more so that more fuel mixture or air can pass through the valve. The valve lift can be increased through the use of higher lobes on the camshaft, and/or more powerful rocker arms. Increased valve lift increases airflow up to a certain extent that you need more lift from the performance cam. However, airflow will eventually peak out because of the restrictions within the cylinder head, in the intake and exhaust systems. The increase in valve lift above this point is not worthwhile since there’s nothing else to gain.

There are physical limitations in the amount to which valves are able to be opened before it causes interference issues between the pistons and valves and between the springs of the valve retention devices and tops of valve guides, and also between the valve’s coils and the springs.

Modifications are possible to improve levels of clearance (such as cutting bigger valve recesses into the tops pistons, or reducing the elevation of the guides for the valves or lowering the spring seats) however, at some point, the limit will be reached, beyond where additional increases in lift of the valve can be physically achievable.

Today, many cams have “asymmetrical” grinds, which use different profiles to create the downward and upside ramps on the cam’s lobes. They also have different lobes to accommodate vent valves.

The sole way to boost the airflow further is to keep the valves open for a longer time (increase the duration) by opening them earlier before closing the valves later or by enhancing the scavenging ability of the exhaust in order to pull the mixture of fuel and air across the chamber of combustion, by increasing the overlap of the valves. There’s a lot of scientific research to determine the optimal valve lift and also how fast the valves close and open. Ideally, you’ll need a quick-acting cam which opens and closes valves swiftly to ensure maximum the flow of air. Also, you need the cam to hit the highest lift as fast as you can, even though the mid-lift airflow is more influential on airflow overall since it occurs twice in every valve cycle (once when the valve opens, and then when closing).

Therefore, you need cam lobes that can open the valves swiftly, keep the valves open at times when the flow of air is highest and close the valves swiftly so that compression losses are minimized. When using flat tappet cams the curve of the ramp that is on the opposite side (flank) that opens the valve opening the valve must not be too steep, or the lifter might be able to dig into the ramp. Also, on the opposite side of the lobe, it isn’t allowed to be too steep, or the lifter might not follow the lobe’s path and bounce back down.

Roller cams are superior in this regard because a roller located at the lower part of a lifter will have a more radical contour of the lobe. The roller cam is able to open and close valves more quickly, allowing for greater airflow while maintaining the same level and length.

Valve Timing Problems

Valve timing is the time when intake valves open , and close, and when exhaust valves open and close. From these four timings closing the intake valve is the most significant one, affecting the amount of power a particular camshaft produces. If the valve shuts down too quickly it could cause the cylinder to not be filled completely with it’s intake stroke.

The intake valve being open longer will allow more airflow into the cylinder up to a certain point. In the event that the intake valve stays open for too long after the point at which the piston is at or reached the bottom dead center the upward motion of the piston could begin to reverse the flow of air and push it back out through an intake port.

The moment at which the valve for exhaust opens is the second biggest influence on its performance. If the valve for exhaust opens too quickly, the pressure in the cylinder might lose pressure before the valve is able to finish its job. If the valve to exhaust is closed too late in its exhausting stroke, it can increase the effort needed to pump to pull away the exhaust from the cylinder.

Did You Know? supply the latest Honda N1 camshafts GSC.

Closing the valve for expulsion as well as that of the valve opening for intake in contrast are the most insignificant on the performance. If the valve for exhaust closes too fast, some exhaust could remain in the cylinder, which could reduce the amount of fuel/air mixture that is incoming when the intake stroke follows. The valve being open longer (even when the intake valve begins to close) causes a scavenging effect that allows air to flow through the cylinder to the exhaust, however you shouldn’t have too much overlap between the valves since this could deprive some of the mixture of fuel and air that could otherwise stay within the cylinder (it can also increase the emissions from exhaust).

In the case of an intake valve, the opening needs to be done in a timely manner so that the cylinder can fill up with fuel mixture and air However, if it begins to open too early (before the dead center of the top) you could have reversionary airflow returned to the manifold that is inlet to intake.

The moment at which intake or exhaust valves are opened or close, is measured by ramps on the lobes of the cam. When the follower or the lifter reach the point at which the ramp begins from the base circle of the lobe The valvetrain starts to move, and then it begins in the process of opening the valve. The point of opening can be measured at a certain level of elevation (such like .004″ (or .050″) as well as referred to as lasting for a certain number of degree of rotation on the crankshaft.

For instance, a street cam could have a stated duration of 224 ° for the intake or exhaust valves that are measured by .050″ in lift with the maximum lift being .470″ (with the stock 1.5 in. ratio the rocker arm).

The lobe separation between top lift points of valves for exhaust and intake may be as high as 110 degrees. The street cams as well as cams specifically designed to generate higher torque from the low to mid range generally have less overlap and greater than one lobe, while cams made for maximum power at high speeds are more overlapping and have less separation between the lobes.

Confusion in Calculations

Comparing one cam grind with one another is difficult since camshaft manufacturers typically measure their specifications for cams in different ways. If duration is measured as .004″ of lift instead that .050″ in lift, this increases the numbers, making the cam appear larger.

It is therefore important to determine where lift is measured in comparing advertised camshaft specifications. In general, the longer the time period, the higher the rpm range in which the cam produces power. Short duration cams are ideal for low speed performance and throttle response. On the other hand, longer duration cams are ideal for high torque for high revving engines that require to produce a lot of top-end power.

Cams that have durations in the range of 195 to 210 degrees (measured as .050″ Cam lift) generally considered to be the ideal for engines that are stock and models that have computerized engine control. When you exceed the 210-220 degree duration, the intake vacuum begins to decrease. This affects the quality of idle and can affect the performance of computerized engines control systems.

Performance cams generally have durations between 220 and the 280 degree mark or more. The longer the time period, the more rough the idle and also the more the power range of the cam on the scale of rpm. A cam that has an endurance of 240 degrees or more will usually produce the greatest power between 3,500 and 7000 RPM.

There’s more to the camshaft choice than just the length and lift. Cams manufactured by two different companies could have similar specifications for duration and lift but they will have very different performance characteristics due to how the camshafts are designed. A significant amount of research and development has been focused on re-designing the lobes’ profiles in recent times to improve performance. Many manufacturers have launched new products that reflect these changes.

Certain cam lobes might have ramps that are steeper or more shallow to alter the speed of the valves opening and close. Rapid opening rates are good provided that the valvetrain and springs are robust enough to withstand the speed. The ability to close the valves fast is also a good thing, however it’s not recommended in the event that the valves close too quickly that they bounce when they touch their seats, or the lifters are able to follow the down slope in the lobe of cam.

A lot of cams today come with “asymmetrical” grinds that employ various profiles on the downside and upside ramps of the cam lobes and distinct lobes to accommodate inlet and exit valves. Some cams also have differently-groomed engines cylinders dependent on the location the location of the cylinder within the block of engine.

The end cylinders of an engine with only one manifold for the carburetor typically will benefit from a bit more length of a valve for the ends cylinders, to ensure that airflow is equalized across the intake manifold. This is a technique that NASCAR has employed for many long and is now accessible in several off-the-shelf line of products.

Make the Right Choice

Selecting a camera randomly from a catalog on a site that lists hundreds, if not hundreds, of grinds to choose from is a daunting process. The model you select might not produce the results you’re looking for, so make sure to read the fine print on every grind, and then look over the recommended specifications. The supplier of the cam might state the particular grind is best suited to specific piston, cylinder head and intake system configurations.

There are a variety of software programs available to aid you in choosing a cam based on information you input into the software. The program recommends a camera that is most compatible with the data you’ve entered. It will also plot simulated torque and horsepower plots to show the performance of your engine you’re creating. While not 100% precise, these programs can perform a decent job of guiding you towards the most appropriate cam.

The best option however is to speak directly to the supplier of your cam when you are choosing the right camera. Many cam vendors will be more than eager to assist you with the selection of a cam.

They will provide you with a comprehensive questionnaire to fill in to determine the specifics of your engine to ensure that a cam is selected that offers the most efficient performance all around for the engine you’re creating. The details cover every aspect of engine displacement to the cylinder heads the compression ratio inlet and exhaust system, whether naturally aspirated or increased, manual or automatic transmission the torque converter’s stall speed and the gear ratios of manual transmissions and differential ratios, as well as tire size , to the type of cam/lifter configuration you’d like (flat tappet roller, solid or hydraulic) to details about how the engine is going to be employed (street street/strip, circle race track off-roading, road racing towing, pulling marine, RV or) according to the year, make and model as well as the size of the vehicle the engine is to be put into.

If you’re looking to gain an advantage over your competition You could opt to create an individual cam ground built for your engine.

It could also require additional precise information like airflow numbers for every increment of valve lift through the cylinder heads rod stroke length and diameter, the brands of rods, pistons, or other components that are used, and so on.

The more detailed information you give to the manufacturer of the cam and the more accurate they are to make a customized cam for your engine.

Certain cam manufacturers have utilized data recording to improve the performance of a customized cam for a client. They set up the data logger with the intention of recording the engine’s rpm when a car is racing and then analyse the speed of the engine through straights as well as into and out of the corners to identify where the engine requires the most power.A Cam grind chosen to make the most power output at the speed range in which it truly needs it. A larger cam could produce more power overall but when the engine isn’t revving enough to make use of that additional power, it’s greater than what the engine actually requires.

It’s best to get an engine that works at the optimal rpm rather than selecting one that is able to produce huge numbers, but fails to make it to the top of the track.