Cam Tech Thread

Post or link any and all info regarding cams. Discuss.

To start out. Some diagrams sourced from Comp.

Lobe Diagram



The terms:

advance – Most commonly refers to combustion timing. Engine timing advance refers to crankshaft timing with regards to achieving piston Top Dead Center (TDC) prior to the combustion event within a cylinder. With regards to advance for camshaft timing – another meaning is the relationship of the intake centerline to TDC of the piston

area under the curve – Describes what a valve-lift cycle would look like if plotted on a graph with time in crank degrees running horizontally and valve lift in thousandths of an inch running vertically. The more quickly the valve opens and dwells in that position, the greater the space from opening to closing or beneath the curve.


cam button – A component that fits into the center of the timing gear and contacts the back of the timing chain cover to reduce the endplay of the camshaft. The cam button needs to be held in with a plate or have some way to keep it in place.

camshaft degreeing – The process of measuring the exact degree position of the camshaft relative to the combustion cycle. This allows for proper timing adjustment to tailor the performance characteristics of the engine.

closing ramp – The end of the valve-opening event, which defines how the valve is returned to the closed position.

coil bind – The point at which a valve spring can no longer be compressed and becomes a solid mass. Extreme valve train damage can occur at this point.

combustion event – The point in the engine cycle (either four or two) when the ignition is triggered, igniting the fuel/air mixture and driving the piston down within the cylinder.

compression – A mathematical calculation that takes into account bore, stroke and cc of the head, head gasket thickness and deck height to determine the static compression of the engine.

cylinder pressure – An engine uses compression to make engine power. Cylinder pressure is determined by camshaft duration, lobe separation and the static compression figures. Excessive cylinder pressure can lead to detonation and other engine problems.


deck height – The height of the cylinder block surface on which the cylinder head rests. Deck height is measured from the crankshaft centerline to the deck surface. It should be uniform from front to rear and may be corrected by machining if necessary.

duration – The amount of time the lobe is creating lift measured in degrees of camshaft rotation.

endplay – Refers to the movement of the camshaft forward and backward within the camshaft galley. Setting the proper amount of endplay is important to avoid excessive valve train wear and timing chain failure and ensure proper lifter positioning. Endplay can also create distributor spark fluctuations.

engine vacuum – The amount of vacuum generated by the engine within the intake manifold during combustion. Vacuum is altered by the camshaft duration specifications, chiefly as a result of overlap.

hot vs. cold valve lash setting – The lash setting is the mechanical camshaft setting that allows for a measurable distance between the rocker arm tip and valve stem. The cold setting is set before the engine has been operating and is larger than the hot lash setting, which is completed after the engine has achieved operating temperature.

intake centerline – The midpoint of the lobe (which may or may not be maximum lift, since some cams are asymmetrical in design).

installed height – The overall measurement of the valve spring when installed from the spring seat to the top of the retainer.

journal diameter – The cross sectional diameter of the cam bearing journal.

lift – The amount of travel by the lifter from the “zero location” on the camshaft up to the nose of the cam lobe. That measurement multiplied by the rocker arm ratio generates the total valve lift figure.

lifter preload – The initial pressure applied to the lifter most often through the rocker arm system.

lobe separation angle – The number of degrees between the intake and exhaust lobe centerlines.

milling – The process of removing, with carbide cutters, a thin layer of metal from the surface of a head or block deck. This is done to restore the flatness of the surface and/or remove material for increased compression.


piston to valve clearance – The clearance between the valve and the piston when the two are at their closest point.

opening ramp – The section of the camshaft lobe between the base circle and the lobe peak.

open pressure – Spring pressure created when the valve is open. There needs to be enough pressure at this point to generate valve train control.

O.D and I.D. – Outside diameter and inside diameter measurements.

ramp speed (aggressiveness of lobe profile) – Refers to the ramp angle of the camshaft lobe. The more aggressive the lobe ramp, the faster the valve opens and closes.

retard – The opposite of the advance event; refers to something that occurs after the combustion event within the cylinder.

rocker arm ratio – The differential between the pushrod and valve stem side of the rocker axis point, expressed as a ratio.

seat pressure – The pressure most commonly in pounds per square inch – exerted on the spring seat. This can be during rest – when the valve is closed.

shim – A thin flat disc in varying thicknesses used to adjust (compress) the valve spring’s installed height.

single and dual pattern camshafts – When the intake and exhaust specifications (lift and duration) on the camshaft are the same, this is a single pattern camshaft. When the intake and exhaust specifications are different, this is a dual pattern camshaft.


symmetrical vs. asymmetrical lobes – When the opening and closing halves of the camshaft lobes are different, they are called asymmetrical lobes. Generally, the opening ramp is more aggressive on these lobes with a longer, slower closing ramp.

split duration camshaft – A camshaft where the intake and exhaust duration specifications are different.

Top Dead Center (TDC) – The highest point achieved by the piston travel within the cylinder bore.

valve float – The point at which the intake lifter and the camshaft lobe are not tracking at the same moment. This is an extremely dangerous event and can, in its most extreme condition, cause valve contact with the piston. Regardless, the peak engine efficiency is not present.

valve lash – A measurement taken between the tip of the valve stem and rocker arm tip. Valve lash is always measured with the lifter positioned off the lobe of the cam. This measurement is taken while adjusting a solid lifter valve train.

valve margin – The distance from the face of the valve straight up the side of the valve to the bottom edge of the valve seat.

valve overlap – This is a function of both duration and lobe separation angle. If the lobe separation angle remains the same but you increase the duration, the amount of overlap will also increase. Overlap is the time, measured in crankshaft degrees, when the exhaust valve and intake valves are both open.

valve train – Valve train is an all-encompassing term used to describe the mechanisms and parts that control the operation of the valves.

LSA effects (Lobe Seperation Angle)




What is the difference between different Lobe separations?

Tighter lobe separation tends to narrow the power band and typically increase the peaks. Tighter separation will also increase cylinder pressure and increase bottom end torque. Narrow also reduces piston to valve clearance, hence too narrow creates many issues with fitment. Also, narrow will decrease engine vacuum at idle and may cause issues with misfire. And, wider lobe separation will do the opposite of the points on tighter separation.

Cam Timing Effects




What is the difference between different Intake Centerlines and how is this not the same as lobe separation?

By advancing and retarding a cam, you can move the ICL wherever you would like, but unless you have separate cams for the intake and exhaust (like the DOHC Ford) you cannot change the lobe separation once a cam is ground. Advancing the cam will make more cylinder pressure and build bottom end while retarding will broaden the power band and add top end, but can also make the motor a little lazier on the bottom.



VCT/Cam phasers.




What are cam phasers?
Ford’s cam phasers are specially designed, computer-controlled cam gears for all 2005 and newer Ford Modular 3 Valve engines that have the ability to adjust camshaft position while the engine is running. Since the modular engine uses two camshafts, two cam phasers are used.

How do they work?
Engine oil is pressure fed to the cam phasers through a series of passageways in the cylinder heads and camshafts. The engine computer controls a pair of solenoids that adjusts this oil flow into and out of the cam phaser’s control chambers, giving the ability to retard the cams up to 60 crank degrees.

Why did Ford put them in the engine?
When the cams are retarded 20-40 degrees during part throttle engine operation, it takes less power to turn the engine over. This helps to increase the engine’s fuel efficiency. Another power benefit is that the cam phasers allow the camshafts to always be in the best position for maximum power, regardless of what the engine’s rpm is. The engine makes more torque and horsepower and extends the high rpm powerband by an extra 800-1000 rpm.


Why should I modify the cam phasers with a COMP Cams® Limiter Kit?
If there is a downside to the stock cam phasers designed by Ford, it is that they have such a wide range of movement. Since the cams can theoretically be retarded by up to 60 degrees, there is very little piston to valve clearance in the engine. This minimal piston to valve clearance limits us to fairly small cam profiles with very little overlap.

What does the COMP Cams® Phaser Limiter Kit do?
These limiter plates replace the factory back-plate on the cam phaser. They have posts which extend into the cam gear’s control chambers, limiting their movement to no more than 20 degrees. This gives more piston to valve clearance and lets you install bigger, more powerful camshafts with safe piston to valve clearances. While keeping up to 20 degrees of movement available, all the wide-open throttle benefits of the cam phasing are retained, since the normal retard the cams see at wide-open throttle is only around 9 degrees.

Do I have to reprogram my engine’s computer after installing the Cam Phaser Limiter Kit?
Yes, you MUST reprogram your engine’s computer for the engine to operate properly after installing the cam phaser limiters. The guidelines for reprogramming are simple – just make sure that the maximum retard amount entered for any of the cam phaser tables and DTC strategies in your tuning software does not exceed 20 degrees.


Why can’t I just reprogram the ECU to limit cam phaser movement?
Since Ford’s factory engine computer is fully programmable, the question arises as to why you can’t simply program in cam phaser limitations and not bother with mechanically limiting the cam phasers? Theoretically you could do that, but a problem arises if something happens that would cause the engine’s rpm to shift faster than the cam phaser controls can react. For example, if you ever missed a shift, broke a driveline part, did a clutch dump on a sticky set of slicks, or anything that could, for a split second, cause the cam phasers to get out of their programmed limits, the valves could crash into the pistons. By mechanically limiting the maximum movement of the cam phasers, total engine safety is assured regardless of the performance level/specs offered by the camshaft.



Why can’t I just mechanically pin/lock the cam phasers?
While you certainly can do that, you are basically taking a step back in terms of making maximum power with your engine. If you lock the camshaft phasers in place, you will typically lose at least 20 hp or 20 ft. lbs. of torque, depending on the degree settings for your camshafts. The main reason so much power is lost is due to the fact that when you lose the ability to retard the cams at high engine speeds, there is a tremendous reduction in power producing airflow. The VCT (variable cam timing) technology is an incredible step forward in delivering both optimum torque and horsepower – a combination performance cam designers have always dreamed about. Why would you pass up the added performance this technology affords by locking it out?

Comp Cam specs

NSR cams.

VSR cams.

SPR cams.

Sub'd Thanks a million.

STICKY if this continues.

UltraKla$$ic said:

Sub'd Thanks a million.

STICKY if this continues.

Click to expand...

Not a bad idea.

Also everyone can post up tech oriented cam questions here.

Lightblade said:

Not a bad idea.

Also everyone can post up tech oriented cam questions here.

Click to expand...

OR you can post up your own Q&A's, in detail, which would be invaluable to us neophites and keep the chatter down to a minimum.

Pure resource from a reputable/knowledgable forum member.

Valve Springs.


Valve springs are one of the most critical and most overlooked components in your engine. Proper selection of the valve spring begins with identifying the application and selecting all of the valve train components to achieve the engine builders’ goals.

The spring is selected to complement the system and must be matched with the entire valve train in order for the engine to reach its full potential. It does absolutely no good to install a cam that will rpm to 8000 if you do not have the correct springs. Improper selection of the wrong valve spring is one of the most common causes of engine failure. Other common causes are the incorrect installation and improper handling of the valve springs.

Selecting a Spring

Proper Spring Handling

Checking Loads

* NOTE *
Since the retainer is installed in the spring when checking the spring loads, make certain that the thickness of the retainer is not included when calculating the installed height and is accounted for when compressing the spring. The spring load checker will show to be higher with the spring installed at the correct height.


Installation

Breaking In a Spring

1. It is important for new springs to take a heat-set. Never abuse or run the engine at high rpm when the springs are new. Upon initial start-up, limit rpm to 1500 to 2000 until the temperature has reached operating levels. Shut off the engine and allow the springs to cool to room temperature. This usually will eliminate early breakage and prolong spring life. After the spring has been “broken-in”, it is common for it to lose a slight amount of pressure. Once this initial pressure loss occurs, the spring pressure should remain constant unless the engine is abused and the spring becomes overstressed. Then the springs must either be replaced or shimmed to the correct pressure.





Q. Why should I replace my factory valve springs when I upgrade my engine?

A. Factory valve springs are adequate for stock engines, but as with most factory components, they are mass produced and performance is often secondary to cost. Once you begin to modify an engine it places added stress on every part of the valve train system. When you upgrade your camshaft even to a mild street performance grind, you increase valve lift, opening/closing aggressiveness, duration and the rpm range of your engine. All of these factors directly affect valve movement, which your valve spring is tasked with properly controlling. This is why it is so important to use quality high performance valve springs, retainers and valve locks from a reputable manufacturer. COMP Cams valve springs utilize only the finest wire material available, latest designs and advanced manufacturing processes, yielding the best performing and most durable valve springs in the industry. While it is hard to visually see the difference between a “low buck” valve spring and a quality valve spring, rest assured that your valve train will know the difference. Choosing to save a few dollars on inferior valve springs is a high stakes gamble with serious consequences.



Q. What is the proper break-in procedure for new valve springs?

A. It is important for new valve springs to take a heat-set. Never abuse or run the engine at high rpm when the valve springs are cold. During the installation process use COMP Cams Valve Train Assembly Spray (#106) on the springs, rocker arms and pushrods to supply the necessary lubrication for the initial start-up. Upon initial start-up, limit rpm to 1500-2000 until the temperature has reached operating levels. Shut off the engine and allow the springs to cool to room temperature. This process will help eliminate premature failure and prolong valve spring life.



Q. What are the main causes of valve spring failure?

A. The most common causes of valve spring failure can be traced to three areas: misapplication, mishandling and improper installation. When selecting valve springs it is necessary to consider camshaft specifics, intended rpm and valve train mass. If you take a valve spring beyond its operating range the results can be catastrophic. All valve springs should be handled with care to avoid stress fractures or scarring of the spring material. Improper installation of a valve spring can cause anything from changes in spring pressures to coil bind issues, ultimately resulting in premature failure. Proper installation and installed height will provide correct seat/open pressures. It is critical that each one of these areas is well thought-out to achieve peak valve spring performance and service life.



Q. Will I have to do any machine work to the cylinder heads when I upgrade my valve springs?

A. COMP Cams offers an extensive line of valve springs, including single, dual, triple, and Beehive designs. For most applications we have springs available which simply drop into place, requiring no additional modifications. Some factory cylinder heads feature small diameter spring pockets and/or tall valve guides which limit the amount of duration and valve lift before retainer-to-valve guide clearance or coil bind becomes an issue. In these cases the spring pocket and/or the valve guide must be modified to make room for a larger diameter valve spring. COMP Cams carries spring pocket cutting tools with detailed instructions to perform this procedure.

A mod can clean up my comments so this thread can be a total resource without chatter but NICE WORK. Keep going!!!!!!!!!!!!!!

Much needed and appreciated!

3v cam install (thumpers)




127500 spr cams dyno pull sound/hp

Nice thread Jeremy. Cam timing events are something I really want to know more about. Especially with 3v's and vct.

Cam selection Q and A


1. How do I go about selecting a cam based on my desired engine rpm range?

Many variables determine the rpm range and torque curve –the “powerband” of an engine, including cubic inch displacement, cylinder head characteristics, intake manifold, camshaft specifications and others. Note that larger displacement engines require more duration than smaller ones because they require more air/fuel mixture to fill their larger displacement cylinders.

The most important aspect of camshaft (and other component) selection is to have your specific rpm “goal” in mind before you begin to select engine parts. A camshaft should be close to the last item on your list –chosen to match all of the other performance pieces on your engine. Remember that the best way to select a camshaft is to ask an expert to help you select the right camshaft based not only on the size of your engine, but on your entire combination of parts.

When seeking assistance in selecting a camshaft, it is important that you can provide the weight of your vehicle, transmission type, converter stall speed, rear end ratio, engine displacement, compression ratio, and whether it will be normally aspirated, or if you intend to run a power adder such as nitrous, a turbocharger, or a supercharger. Each of these variables must be considered when choosing a cam, and the more accurate the information – the better your new camshaft will perform.

2. What is the difference between intake centerline and lobe separation angle?

These two terms are often confused. Lobe separation angle (LSA) is simply that: the number of degrees (denoted by the ‘°’ symbol) separating the peak lift points of the intake and exhaust lobes. Lobe separation is effectively “locked in” when a camshaft is ground and cannot be changed. Note that a tighter lobe separation (smaller LSA number) results in a narrower and peakier torque curve, and a wider lobe separation (larger LSA number) produces a broader torque curve.

The intake centerline is the position of the centerline (or peak lift point) of the intake lobe in relation to the Top Dead Center position of piston travel. Intake centerline can be adjusted by degreeing your camshaft, and can have the effect of increasing off-idle torque (advancing) or increasing peak RPM (retarding) .

For example, if your camshaft has a 110° LSA, and you install it with 4° advance, your intake centerline is 106° after Top Dead Center.

3. My motor is currently naturally aspirated, but I plan on installing a power adder. Can I use the same cam for both applications?

Normally aspirated (N/A) engines and boosted engines generally require different camshafts for optimum efficiency. Typically, camshafts intended for use with power adders will feature a wider LSA and more exhaust duration than those intended for use in a non-boosted application.

A few important points:
4. How does increasing or decreasing duration affect my engine performance?

Duration has a tremendous amount of affect on engine behavior -most notably, the rpm at which its peak torque is produced. Shorter duration camshafts (or “mild” cams) produce more low rpm torque, while camshafts with larger duration (or “bigger” cams) will tend to increase upper rpm horsepower at the expense of low rpm torque. In general, for every 10° increase in duration, the torque peak of the engine moves up by 500 rpm.

5. I currently run a solid flat tappet cam. Is it worth the investment to upgrade to a solid roller cam?

The simple answer to this question is yes -if it’s in your budget. Solid roller designs use the latest and most advanced profiles that we offer. Among the benefits are reduced valve train friction, higher engine rpm capability, and use of faster ramp profiles, which generate higher power and torque by snapping the valve open and closed more quickly.

Solid roller camshafts and related component technology has come a long way in the last 10 years. Today, a solid roller setup can be durable and offer incredible performance. COMP Cams® offers a high quality, Endure-X™ lifter which features a tool steel axle, EDM Oil Injection and precision sorted needle bearings. Endure-X™ lifters are available for a variety of engines with different offsets and lifter body heights.

6. How does compression ratio affect camshaft selection?

The key factor to consider here is cylinder pressure. If you have a lower compression motor, say 9.5:1, and you use a camshaft that is fairly large (increased overlap between lobes –which allows both the intake and exhaust valves to be open at the same time) then you will bleed off cylinder pressure and in effect – horsepower and torque.

On the other hand, if you’re running a high compression race motor and your camshaft has a minimal amount of overlap, the cylinder pressures can go sky high. This is far less of a problem for race engines than it is for street-bound engines, but it should be considered and factored in at the time that you choose your cam. In addition, the type of cylinder heads that you’re using and the quality of available fuel should be taken into consideration. If you have to stick with pump gas, the rule of thumb is to limit compression to 10:1 with cast iron heads and 11:1 compression with aluminum heads.

Great info thanks for posting Jeremy. Subd'

BZ Jeremy!

Now we need a sub thread on why the Hot Rod/Detroit Rockers would not work well with FI.

Also something cool to note about the new tivct dohc 4v vs. vct in the ohc 3v.

Tivct allows for not only cam timing advancing or retarding but because its can be changed indpendently this also allows for dynamic changing of effective lobe seperation angle. Instead of this value being fixed on a single cam setup that has intake and exhuast lobes on the same camshaft.

Allows you to be at peak efficiencey and performance everywhere in the rpm range. And allows you to custom tune the stock cams for a wide array of applications be it n/a, supercharger or turbo.

Ehhh...I would not mix apples and oranges unless you want to make a fruit salad.

This stuff is hard enough to understand without getting the Tivct involved.

Greg Hazlett said:

Ehhh...I would not mix apples and oranges unless you want to make a fruit salad.

This stuff is hard enough to understand without getting the Tivct involved.

Click to expand...

LOL

great info. sticky this please. nice lightblade