Camshaft Information and Specifications

Discussion in 'Fox 5.0 Mustang Tech' started by 5spd GT, Nov 21, 2007.


  1. 5spd GT

    5spd GT "the 5.0 owns all" Founding Member

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    There is much to be edited and added, so I am not finished. I hope this helps you guys out as I build it up:) If corrections need to be made, feel free to let me know.

    Post One will include terms and valve timing explained along with extra links.

    Post Two will be continued and include common 5.0L camshaft specifications.

    After reading much of the following, you will quickly realize that a camshaft is the brains of an engine and how IMPORTANT it is to get a camshaft to match your goals and engine combination. This is where custom cam grinders shine:nice: Contact either of the following to find out more, and how it is money well spent.

    Ed Curtis ([email protected]) @ www.flowtechinduction.com
    Buddy Rawls ([email protected]) @ http://www.wighat.com/fcr3/index.html

    Camshaft Term Glossary

    ABDC:
    Degrees after bottom dead center.

    ATDC:
    Degrees after top dead center.

    AREA UNDER THE CAM LIFT CURVE:
    The area under the bell shaped curve with lift on the vertical axis and degrees of rotation on the horizontal axis. The greater the area under the lift curve, the greater is the lift and/or duration at some point on the camshaft profile.

    BASE CIRCLE:
    The concentric or round portion of the cam lobe where the valve lash adjustments must be made. (Also known as the heel.)

    BBDC:
    Degrees before bottom dead center.

    BTDC:
    Degrees before top dead center.

    CAM FOLLOWER/TAPPET:
    Usually a flat faced or roller companion to the camshaft that transfers the action of the camshaft to the rest of the valve train by sliding or rolling on the cam lobe surface.

    CAM LIFT:
    This is the maximum distance that the cam pushes the follower when the valve is open. This is different from valve lift. See "GROSS VALVE LIFT."

    CAM MASTER:
    After the design of the cam is computed, it is transferred to a precision template or master. The master is then installed in the cam grinding machine to generate the shape of the lobes of the production cam.

    CAM PROFILE:
    The actual shape of the cam lobe.

    CAMSHAFT:
    A shaft containing many cams that covert rotary motion to reciprocating (lifting) motion. For every 2 revolutions of the crankshaft, the camshaft rotates 1 revolution. The lobes on the camshaft actuate the valve train in relation to the piston movement in an internal combustion engine. The camshaft determines when the valves open and close how long they stay open and how far they open.

    CARBURIZING:
    Gas carburizing is a method to heat-treat steel camshaft billets. In this method, the camshaft is placed in a carbon gas atmosphere furnace and heated to the proper temperature. When the shaft has absorbed the proper amount of carbon, it is removed from the furnace and quenched to the proper temper.

    CAST BILLET:
    A term used to describe a camshaft that is made from a casting. The material for the casting is a special grade of iron alloy called "Proferal." GLOSSARY OF CAMSHAFT TERMS (CONTINUED)

    CHEATER CAMS:
    See "Improved Stock Cams".

    CHILLED IRON LIFTER:
    A cam follower made from high quality iron alloy that is heat treated by pouring the molten iron into a honeycomb mold with a chilled steel plate at the bottom to heat treat the face of the lifter. It is compatible with steel and hardface overlay cams only.

    CLEARANCE RAMPS:
    The portion of the cam lobe adjacent to the base circle that lifts at a constant slow speed. It's purpose, in theory, is to compensate for small deflections and take up the slack in the valve train created by the valve lash. The opening ramp takes up all clearances in the valve train and causes the valve to be on the verge of opening. The closing ramp begins when the valve touches the valve seat and ends when the tappet returns to the base circle. Ramp designs have a tremendous effect on power output and valve train reliability.

    COIL BIND:
    A valve spring that has been compressed to the point where the coils are stacked solid and there is no space left between the coils. The valve cannot open any further at when this happens.

    CONCENTRIC:
    Running true or having the same center. In camshaft terminology, the cam bearings and lobes are concentric to each other when the cam is straight and there is .001" or less runout between all the cam lobes and bearings.

    DURATION AT .050":
    The amount of time measured in degrees of crankshaft rotation from when the valve is open .050" far until it is .050" from closing.

    FLAME HARDENING:
    A heat treating process whereby a camshaft is exposed to an open flame and then quenched (cooled in oil).

    FLANKS:
    The sides of the cam lobe or the portion of the lobe that lies between the nose and the base circle on either side.

    GROSS VALVE LIFT:
    This is obtained by multiplying the cam lift by the rocker arm ratio. Rocker arm production tolerances can vary this figure by as much as +/- .015".

    HARDENABLE IRON LIFTERS:
    A cam follower made from high quality iron alloy. This special alloy is compatible with cast iron billet camshafts. The entire body of the hardenable iron lifter is hard as compared to the chilled iron lifter where only the base is hardened.

    HYDRAULIC VALVE LIFTERS:
    These lifters are designed to maintain zero lash in the valve train mechanism. Their advantages include quieter engine operation and elimination of the periodic adjustment required to maintain proper lash as with solid valve lifters. Hydraulic lifters do, however, maintain a constant pressure on the camshaft, which solid lifters do not; therefore, the antiscuff properties of lubricating oils are more critical with hydraulic lifters.

    IMPROVED STOCK CAMS (CHEATER CAMS):
    The improved stock cam has stock lift and duration but the flanks are modified so that they are faster acting. This process adds about a 5% increase in the area under the lift curve. This means there will be a power increase during the entire RPM range of the engine. This type of grind works very well in engines that have fuel injection systems that run off of manifold vacuum and are therefore very sensitive to camshaft duration changes.

    INDUCTION HARDENING:
    A process of electrical heat treating whereby an object is placed inside a coil of heavy wire through which high frequency current is passed. Through the electrical properties of this induction coil, the object inside the coil becomes cherry red almost instantly and is then quenched in oil.

    INTERFERENCE FIT:
    In a dual spring combination where the outside diameter of the inner spring and the inside diameter of the outer spring nearly approximate each other so that there is a slight press fit between the 2 springs. This produces a dampening effect on valve spring vibration and surge.

    LASH (VALVE LASH):
    This is the clearance between the base circle of the camshaft lobe and the camshaft follower or tappet.

    LIFT GRAPH:
    By installing the camshaft in a block or head, the mechanic can plot the lift of the cam in relation to each degree of camshaft rotation by installing a dial indicator on the cam follower or tappet and a degree wheel on the crankshaft. All that is necessary is to rotate the crankshaft every 5 degrees and take a reading on the dial indicator at each of these intervals and transfer the readings to the graph paper.

    LIFTER PRINT (CAM PRINT):
    The amount of travel the cam lobe has across the lifter face. Lifter diameter determines flank velocity.

    LOBE:
    The lobe is eccentric to the cam bearings of the camshaft and transmits a lifting motion through the valve train to operate the valves. The design of the lobe determines the usage of the camshaft. (I.e. street use or all out competition).

    LOBE CENTERS-CAM:
    The distance measured in degrees between the centerline of the intake lobe and the centerline of the exhaust lobe in the same cylinder.

    LOBE CENTERLINES-VALVE:
    The point at which the valve is fully open. For example, full intake lobe lift at 110 deg. ATDC. full exhaust lobe lift at 110 deg. BTDC. This camshaft was ground with 110 deg. lobe centers and is timed straight up. It is neither advanced nor retarded. Another example, full intake lobe lift at 105 deg. ATDC. full exhaust lobe lift at 115 deg. BTDC. This camshaft was ground also on 110 deg. lobe centers but is advanced 5 crankshaft degrees.

    LOBE TAPER:
    This is the amount by which the diameter of the front of the base circle is different from the diameter of the rear of the base circle. The amount of taper can be anywhere from zero to .003" depending on the engine. If the forward side of lobe is greater than the rear side we say that the cam has taper left (TL). If the back side of the lobe is greater than the front side then we say that the cam has taper right (TR). Lobe taper has a dramatic effect on the speed of rotation of the lifter. If the lifter does not rotate at the proper speed, premature lifter and cam wear will occur.

    NET VALVE LIFT:
    The actual lift of the valve. This lift can be determined by subtracting the valve lash dimension from the gross valve lift figure. Rocker arm production tolerances can vary this figure by much as +/-.015".

    NITRIDING:
    Gas nitriding is a surface heat treatment that leaves a hard case on the surface of the cam. This hard case is typically twice the hardness of the core material up to .010" deep. This process is accomplished by placing the cam into a sealed chamber that is heated to approximately 950 degrees F and filled with ammonia gas. At this temperature a chemical reaction occurs between the ammonia and the cam metal to form ferrous nitride on the surface of the cam. During this reaction, diffusion of the ferrous-nitride into the cam occurs which leads to the approximate .010" case depth. The ferrous-nitride is a ceramic compound that accounts for its hardness. It also has some lubricity when sliding against other parts. The nitriding process raises and lowers the chamber temperature slowly so that the cam is not thermally shocked. Because of its low heat-treat temperature no loss of core hardness is seen. Gas nitriding was originally conceived where sliding motion between two parts takes place repeatedly so is therefore directly applicable to solving camshaft wear problems.

    NOSE OF THE LOBE:
    The highest portion of the cam lobe from the base circle (full lift position). Overhead cam engine. In this type engine the camshaft is positioned above the valves.

    OHC:
    Overhead cam engine. In this type engine the camshaft is positioned above the valves. (i.e. 4.6 SOHC and DOHC)

    OHV (PUSHROD ENGINES):
    Overhead valve engines. In this type of engine the camshaft is positioned beneath the valves. (i.e. 302 Ford, 346 GM LS1)

    OVERLAP:
    A situation where both the intake and exhaust valves are open at the same time when the piston is at top dead center on the exhaust stroke. The greater the seat duration is on the intake and exhaust lobes, the greater the overlap will be in degrees.

    PARKERIZING:
    A thermo-chemical application whereby a nonmetallic, oil-absorptive coating is applied to the outside surface of the camshaft. This permits rapid break-in without scuffing the cawhere sliding motion between two parts takes place repeatedly so is therefore directly applicable to solving camshaft wear problems.

    NOSE OF THE LOBE:
    The highest portion of the cam lobe from the base circle (full lift position). Overhead cam engine. In this type engine the camshaft is positioned above the valves.

    OHC:
    Overhead cam engine. In this type engine the camshaft is positioned above the valves. (i.e. 4.6 SOHC and DOHC)

    OHV (PUSHROD ENGINES):
    Overhead valve engines. In this type of engine the camshaft is positioned beneath the valves. (i.e. 302 Ford, 346 GM LS1)

    OVERLAP:
    A situation where both the intake and exhaust valves are open at the same time when the piston is at top dead center on the exhaust stroke. The greater the seat duration is on the intake and exhaust lobes, the greater the overlap will be in degrees.

    PARKERIZING:
    A thermo-chemical application whereby a nonmetallic, oil-absorptive coating is applied to the outside surface of the camshaft. This permits rapid break-in without scuffing the cam lobes.

    PROFERAL IRON:
    A very high quality cast iron alloy. Used primarily for camshafts because of its excellent wearing ability.

    ROLLER TAPPET:
    The roller tappet performs the same function as the mechanical or hydraulic tappet. However, instead of sliding on the cam face, the lifter contains a roller bearing that rolls over the cam surface.

    SEAT DURATION:
    The total time in degrees of crankshaft rotation that the valve is off of its valve seat from when it opens until when it closes.

    SPLIT OVERLAP:
    An occurrence when both the intake valve and the exhaust valve are off their seats at the same time by the same amount.

    SPRING FATIGUE:
    Valve springs have a tendency to lose their tension after being run in an engine for certain periods of time, because of the tremendous stress they are under. At 6,000 RPM, for example, each spring must cycle 50 times per second. The tremendous heat generated by this stress eventually effects the heat-treating of the spring wire and causes the springs to take a slight set (drop in pressure).

    SPRING SURGE:
    The factor which causes unpredictable valve spring behavior at high reciprocating frequencies. It's caused by the inertia effect of the individual coils of the valve spring. At certain critical engine speeds, the vibrations caused by the cam movement excite the natural frequency characteristics of the valve spring and this surge effect substantially reduces the available static spring load. In other words, these inertia forces oppose the valve spring tension at critical speeds.

    The above terms that are commonly tossed around about camshafts is courtesy of Elgin Cams.

    Now we need to try to put all this together in finding out how it relates to engine performance. So the following segments will be to help in seeing how a typical 4 stroke engine works.

    Timing Tutorial Help:

    Competition Cams Valve Timing Tutorial

    There are 4 simple strokes to an engine: Power, Exhaust, Intake, and Compression.

    First, there is the power stroke, which is created after the spark ignites the compressed air/fuel mixture the piston is pushed downwards and relates the power to the crankshaft.

    Second, there is the exhaust stroke where the piston is now coming up and the exhaust valve opens to push the excess air out the exhaust port into the exhaust manifold.

    Third, there is the intake stroke in which air is pushed down into cylinder as it travels downward.

    Fourth, there is the compression stroke in which the piston moves upwards to compress the air/fuel mixture that entered the cylinder on the previous stroke.

    One should notice that the intake opening typically happens before top dead center (BTDC) and the intake closing typically occurs after top dead center (ATDC). The exhaust opening typically happens before bottom dead center and the exhaust closing typically occurs after top dead center (ATDC).

    I will discuss this a little better and try to combine the strokes with the valve timing.

    For simplicity I will start with the power stroke. The piston has just been "exploded" downwards to transmit all the power to the crankshaft to rotate it. Before the piston reaches the bottom, the exhaust valve begins to open in order to begin scavenging the exhaust, and after the power stroke passes bottom dead center, the exhaust stroke begins. The reason the exhaust valve will open before the piston reaches the bottom of its travel is because cylinder pressure is much higher, even at this point, than atmospheric pressure. This helps scavenge some of the exhaust out the exhaust port.

    As the piston is coming back up to push out the extra gasses out the exhaust, the exhaust valve opens up fully and then begins to close as the piston approaches top dead center. Just before the piston gets to the top and the exhaust valve closes, the intake valve begins to open. At this point, called overlap, both the intake and exhaust valve are open. The exhaust valve closes a little after top dead center (ATDC), which is when the intake stroke begins.

    The intake stroke is where the intake valve continues to open and air is pushed in from the atmospheric pressure. The intake valve continues to stay open until just after the piston reached the bottom of its travel, (ABDC). After top dead center and after the intake valve closes, the compression stroke begins to compress all the air/fuel that was just entered into the cylinder. The ignition occurs a little before the piston gets back up to the top dead center position, to continue right into the power stroke. The cycle repeats over and over. Next, the individual valve timing will be explained.

    More Individual Valve Timing:

    Intake Opening Events:

    The intake open timing can affect manifold vacuum, throttle response, gas usage, and emissions.

    An early opening intake valve at low speeds, coupled with high vacuum situations can cause exhaust gas reversion to exit out of the early opening intake valve. This happens because as the piston is coming up on the exhaust stroke to push out the extra gasses, it will have enough force to push the exhaust gas into the intake valve, if it opens up to early.

    A later opening intake valve, in conjunction with the exhaust valve timing, reduces the amount of overlap. The later opening intake valve will help at lower RPM and usually helps manifold vacuum, assuming it is in tune with the other valve events.

    The higher the RPM desired for a particular power band the air demand needs to increase. A early intake valve opening allows the incoming air to have more time to fill the cylinder. At higher RPMS, the exhaust gases that are being pushed out help pull some of the early intake air charge out the exhaust valve, and helps get rid of any remaining gasses. This type of purging can lead to a slightly rougher idle and slightly more gas consumption.

    Intake Closing Events:

    The earlier the intake valve closes the more cranking pressure you will get. This leads to what many refer to as more low-end torque and throttle response, which typically will give the engine a broader torque curve. An early intake closing also uses the combustion more efficiently and reduces emissions as well, and therefore helps fuel consumption.

    But when the RPM increases or the power band desired is higher, the incoming air charge has more momentum behind it. This demands a later intake valve closing event to try to get as much air in as possible to be combusted. If the intake valve is closed to late, the once incoming air and all its momentum may have time to escape. Valve timing is critical here.

    The ultimate goal is to get the intake valve to close right as the intake air charge quits flowing into the cylinder. Getting the valve events timed in perfect order is very difficult from a mechanical point of view. The valves cannot open and close like a light switch. They have to be managed smoothly at a certain rate, or you risk valve bounce, excessive valve train wear and noise.

    Exhaust Opening Events:

    In contrast to the intake closing events, the exhaust opening events probably have the least importance in valve timing. As they say though, it is last but definitely not least.

    Cylinder pressure will be decreased if the exhaust valve opens to early. The exhaust valve typically opens near the bottom of the power stroke pushing the piston downwards, so you can see why if you open it up to early it can decrease cylinder pressure. However, the exhaust needs to open up early enough to help gas scavenging for the cylinder that just going through the power phase of the stroke.

    One may see that higher RPM engines will have even earlier exhaust openings because at high RPM, that cylinder pressure is typically already used by the time it gets half-way down the stroke. So, inversely you will see lower RPM engines have a later exhaust valve opening, more near the bottom of the power stroke, keeping increased cylinder pressure longer, in turn, providing a more efficient burn, aka, emissions.

    Exhaust Closing Events:

    An early exhaust valve closing can provide a smoother idle and lower RPM power, which is the same principle that a late intake opening creates. It reduces overlap period, in which both intake and exhaust valves are open, intake opening/exhaust closing.

    It is just the opposite; a late exhaust valve closing is just like opening up the intake valve early. It increases overlap, which if too much can cause the incoming intake air charged to be pushed back into the intake ports of the head. It also can cause the incoming air to be pushed out the exhaust, if the exhaust valve closes too late in relation to the intake valve opening events.

    A late exhaust closing valve is not all bad. At higher RPMS and power bands, it can get rid of the excess gas out into the exhaust port, and also can provide a higher vacuum in the intake at higher RPMS.

    You can see how getting each opening and closing event balanced can effect an engines characteristics.

    Summary:

    If you take these generalities, a camshaft with low-end, broad power band, and good idle qualities will prefer a later intake valve opening, early intake valve closing, later exhaust valve openings, and early exhaust valve closing.

    On the contrary, a camshaft that desires more RPM and a higher power band will prefer early intake valve opening, late intake valve closing, early exhaust valve openings, and late exhaust valve closing.

    Individual valve events are very important in a camshaft and are often overlooked. Of course, they are no the only factor in determining where power and driving quality is made.

    Further Explanation For Camshaft Terms:

    Lobe Separation Angle (LSA):

    Many will see on their camshaft timing card a number labeled as LSA. This is the Lobe Separation Angle. It has many effects on an engine and I will explain what decreasing and increasing LSA can do to the engine parameters. Lobe separation angle defined as a measurement in degrees of the distance between the max lift on the exhaust and intake camshaft lobes, and is measured in camshaft degrees. It cannot be changed once it is ground.

    First off, this is general information and there are other factors, but the following will be a good rule of thumb.

    A 110 degree LSA is considered a tight lobe separation angle compared to a 114 degree LSA.

    A 114 degree LSA is considered a wider lobe separation angle compared to a 110 degree LSA.

    We will use and compare these examples below.

    The tighter LSA of 110 degrees:

    - Increases cylinder pressure, cranking pressure, dynamic pressure, which can increase octane requirements.
    - Increases valve overlap.
    - Narrows the power band, and put torque at a more midrange RPM.
    - Increases speed of engine revving.
    - Initially gives quicker throttle response.
    - Reduces idle quality and creates less vacuum.
    - Decreases piston to valve clearance.
    - Reacts better for carbureted engines.*

    The wider LSA of 114 degrees:

    - Decreases cylinder pressure, cranking pressure, dynamic pressure, which will decrease octane requirements.
    - Decreases valve overlap.
    - Widens the power band, and put torque at a higher RPM being more peaky.
    - Decreases speed of engine revv
    #1
  2. 5spd GT

    5spd GT "the 5.0 owns all" Founding Member

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    LSA Continued:

    So how does one figure out the LSA?

    If you know the Intake Centerline (ICL) and the Exhaust Centerline (ECL), you can add them together and divide by 2, as follows:

    Say you have a 107 ICL and a 117 ECL.

    (107+117)/2 =112 LSA.

    Keep in mind, that a LSA of 112 does not mean the camshaft will act the same as another camshaft with a LSA of 112. The LSA is determined by different valve opening and closing events, figuring out the ICL and ECL from them, and doing the above math. I will use two typical camshafts below, to show how you cannot compare a camshaft based on the LSA alone. It is just a little piece in the design of a camshaft.

    The Ford Racing Z303 camshaft has the following valve events at .050":

    Intake Opening: 7* BTDC
    Intake Closing: 41* ABDC
    Exhaust Opening: 51* BBDC
    Exhaust Closing: 3* BTDC

    IO+IC+One Stroke = Duration for Intake @ .050" or 7+41+180 = 228*.

    EO+EC+One Stroke = Duration for Exhaust @ .050" or 51-3+180 = 228*.

    Now find the ICL and ECL.

    Intake Centerline is found by: (Intake Duration/2) - IO BTDC. In other words...

    228/2 = 114. 114-7 = 107* ICL.

    Exhaust Centerline is found by: Exhaust Duration/2 + EC BTDC. In other words...

    228/2 = 114. 114+3 = 117* ECL.

    107+117 = 224/2 = 112* LSA.

    Now quickly, one can do this for the Lunati 51014 camshaft. It has the following valve timing specs at .050" and a LSA of 112, like the Z303 camshaft:

    Intake Opening: 1* BTDC
    Intake Closing: 37* ABDC
    Exhaust Opening: 49* BBDC
    Exhaust Closing: -3* ATDC

    Intake Duration is 1+37+180 = 218*. The ICL is (218/2)-1 = 108*.

    Exhaust Duration is 49-3+180 = 226*. The ECL is (226/2)+3 = 116*.

    LSA = (108+116)/2 = 112* LSA.

    Now you see that both, the Z303 and the Lunati camshaft have the same LSA, but different individual valve events and ICL/ECL figures. So how can a camshaft with the same LSA, act the same, or idle at a particular level?

    It cannot because of many different factors and an endless amount of possibilities.

    Overlap Period:

    Overlap is close to the same principle of the above LSA information but it is not the same, so do not get it confused. It occurs at the end of the exhaust stroke while the exhaust valve is closing, and when the intake valve is beginning to open when the intake stroke is beginning.

    The main goal of the overlap period is exhaust scavenging and can vary depending on power band desired, along with exhaust pieces used on the engine.

    More overlap (less/narrow LSA), decreases vacuum, but increases the signal relation between the exiting exhaust and incoming intake air charge. This helps acceleration. However, a camshaft with higher overlap periods will not perform as well at lower RPMS, as compared to one with less RPM.

    Less overlap (more/wider LSA), increases vacuum, and helps gas consumption by trapping more gas inside the cylinder, instead of exiting out the exhaust. This helps idle and low RPM quality.

    The below calculations will help, but what really effects the period of overlap and how it effects engine characteristics is the combination of the LSA, duration, and lift. LSA is not the only factor in determining the amount of overlap. The more duration and lift on the cam lobes, the larger the overlap area.

    You can reduce overlap by reducing duration as well, or having a less aggressive camshaft lobe profile. Just as we have discussed, widening the lobe separation angle reduces overlap as well. The inverse applies.

    The intake and exhaust package efficiency, along with how well the incoming air travels over the exiting exhaust and it's valve, help determine what type of overlap can be used for a particular engine combination.

    You will see further below, many 5.0L cam specs. It includes a period of overlap for many of the camshafts. This is figured out, like so:

    - Add the advertised duration of the intake and exhaust lobes.
    - Divide by four.
    - Subtract the LSA.
    - Multiply by two.

    This will give you the period of overlap in reference to the crankshaft degrees.

    Here is a calculator to make it easier:

    http://www.wallaceracing.com/overlap-calc.php

    Base Circle:

    The base circle of a camshaft is the diameter of the cam lobe that does not have any lift. This is where you set-up your valve train, which is on the base circle. In other words, it is the portion of the path around the cam followed by the rocker arm that doesn't generate lift.

    Larger base circles are better for high RPM and higher performing engines. Since a camshaft is turned by the crankshaft, through the connection of the timing chain, it can cause some twist. Most daily driver or street cars do not see any reason to upgrade to a larger base circle, but some serious racers do. There is a lot of stress and pressures on the camshaft from the heavy valve train. A small base circle also creates less wear and does not have as many different lobe profiles as a larger base circle camshaft. Ls1 camshafts have larger base circle camshafts than does a standard 5.0L.

    Gross Valve Lift:

    This is the most commonly referred to lift number. It is a combination of the lobe lift multiplied by the rocker ratio. In general, the more lift, the more torque that is created. What I seem to have noticed is shorter duration camshafts with high lobe lifts typically are designed for daily driver and street car grinds. It helps torque, throttle response, and overall useable power. The valve train needs to be up to par if you decide to go with large lift numbers. Lift is one of the last factors that effect piston to valve clearance.

    Want to know your lift values after a roller rocker change?

    Take your current lift numbers and divide it by your current roller rocker ratio. You then get the lift numbers at the lobe. Take your lift number at the lobe and multiply it by the new roller rocker ratio.

    Example:

    .500" divided by stock 1.6 Roller Rockers = .313"
    .313" x by new 1.7 Roller Rockers = .532"

    More Roller Rocker Information:

    Advertised Duration and Duration @ .050":

    This camshaft specification is often talked about. Duration is in degrees related to crankshaft revolution. It is the degree the crankshaft is rotated, while the lifter is off the base circle of the camshaft.

    A higher duration degree number will do better in the upper RPMS. A lower duration degree number will do better in the low RPMS, all else being the same.

    Advertised duration is more of an old school number and is good in marketing. It is typically a measurement from .004", .006", or sometimes .020" up from the base circle. The latter is a better determiner for seeing how a camshaft may act than the preceding .004" and .006" duration measurement marks. With the different variations, it is not an accurate measurement to compare from camshaft to camshaft.

    Comp typically uses .006" for the advertised duration.
    Crane typically uses .004" for the advertised duration.

    This makes the Crane camshafts appear to have a larger camshaft, since they start measuring the duration before Comp. Just be careful, when comparing different camshafts between different companies.

    One can figure out if a camshaft has a steeper ramp rate by taking the .050" duration numbers on the cam card and using the advertised duration at the same point. No use in comparing a .004" measurement to a .020" measurement.

    Advertised Duration - .050" Duration = Ramp Rate Comparison

    Crane 2030: 270-216 = 54
    Crane 2031: 276-214 = 62

    The Crane 2031 has a milder ramp rate. I used Crane because it is the same company and they compute their advertised duration at .004". A better comparison would be to measure .100" to .050", rather than .050" to .004" measurements, because the latter is lash than anything, which does not translate to the valve because no lift off the base circle has occured yet.

    However, there is a more accurate standard of comparison. It is the duration at .050" that is more accurate and widely used. At .050" off the base circle, this is how many degrees the crankshaft turns from .050" on.

    It is best to have different duration numbers throughout the lift range to actually begin to compare ramp rates. Watch two camshafts from .006", .050", .100", .200", etc., to get a more accurate idea. A cam doctoring machine does this sort of thing very easily.

    This can (but not limited too) help better vacuum, increased throttle response, and a broader power band. The more aggressive ramp rates, lobe profile, acts like a less aggressive camshaft, but creates more "area under the curve," like what a larger base circle camshaft can provide.

    Typically longer duration camshafts and longer periods of overlap allow the ability to run a higher static compression ratio without detonation in the low RPM range. Just as well, running with more duration and longer periods of overlap can be a little slow in RPM buildup at lower RPMS.

    Advancing and Retarding the Camshaft:

    To advance and retard a camshaft you need a multi-index crankshaft sprocket.

    Advancing the camshaft:

    - Begins the intake valve event to open sooner.
    - More low-end power.
    - Decreases intake valve clearance.
    - Increases exhaust valve clearance.
    - Higher compression rating.

    Retarding the camshaft:

    - Begins the intake valve event to open later.
    - More top-end power.
    - Increases intake valve clearance.
    - Decreases exhaust valve clearance.
    - Lower compression gauge reading.

    How are camshaft specifications in degrees, measured?

    Duration - Degrees of crankshaft rotation.
    Valve Opening and Closing Events - Degrees of crankshaft rotation.
    Lobe Centerline - Degrees of crankshaft rotation from TDC.
    Lobe Seperation of Angle - Angle between the intake and exhaust camshaft lobe peaks described in camshaft degrees.

    More Helpful Explanations on Camshafts and Theory:

    How a Camshaft Works

    Camshafts Explained

    Camshafts Explained

    Camshafts Explained

    Buddy Rawl's Camshaft Theory

    Camshaft Question and Answers

    More Camshaft Question and Answers

    Become a Camshaft Expert

    How To Degree a Camshaft

    Understanding Camshaft Specifications

    Stock 87-93 Cam Information:

    Lift is .444*/.444* - Advertised @ 266*/266* until August of '88, then it went to 276*/266* .

    Duration at .050" varies and ranges from 204*+/204*+

    85-88:
    Lift: .278 intake, .278 exhaust
    Duration: 266 intake 266 exhaust
    Overlap: 36 degrees, 9.04 factor
    Lobe Center: 115 intake, 115 exhaust

    89-90:
    Lift: .278 intake, .278 exhaust
    Duration: 276 intake, 266 exhaust
    Overlap: 39 degrees, 19.51 factor
    Lobe Center: 116 intake, 115 exhaust

    91-95:
    Lift: .278 intake, .278 exhaust
    Duration: 276 intake, 266 exhaust (.006)
    Duration: 214 intake, 210 exhaust (.050)
    Overlap: 39 degrees, 19.51 factor
    Lobe Center: 116 intake, 115 exhaust
    Also have read: 118 intake, 113 exhaust

    1.6 Rocker Ratio
    Intake Opening: 11* ATDC
    Intake Closing: 45* ABDC
    Exhaust Opening: 39* BBDC
    Exhaust Closing: 9* BTDC

    Combustion (0-180) - Exhaust (181-360) - Intake (361-540) - Compression (541-719)

    Cam Events at .050":
    Intake Opens - 141
    Intake at Max Lift - 478
    Intake Closes - 585
    Exhaust Opens - 141
    Exhaust at Max Lift - 246
    Exhaust Closes - 351

    More Info:

    F1ZE-6250-AA cam specs:

    Duration 276*/266*
    Lift 0.445"/0.445"
    LSA 115.5*
    ICA 118*
    ECA 113*

    E5ZE-6250-AA cam specs :

    Duration 266*/266*
    Lift 0.444"/0.444"
    LSA 115*
    ICA 116*
    ECA 114*

    93-95 Cobra:
    Lift: .282 intake, .282 exhaust
    Duration: 270 intake, 270 exhaust
    Overlap: 33.5 degrees, 15.24 factor
    Lobe Center: 115 intake, 121.5 exhaust

    1985-08/1988
    I.O. 17 BTDC / I.C. 69 ABDC
    E.O. 67 BBDC / E.C. 19 ATDC

    08/1988 - 1993
    I.O. 20 BTDC / I.C. 76 ABDC
    E.O. 67 BBDC / E.C. 19 ATDC

    Cam - Duration @ .050" - Adv. Duration - Valve Lift - Lobe Lift - LSA - Int./Exh. Centerline - Powerband

    Ford Racing Camshafts

    B303 - 224*/224* 284*/284* - .480"/.480" - .300"/.300" - 112* - 107* ATDC /117* BTDC - 3,300-5,100 RPM
    Overlap: 60 degrees.
    1.6 Rocker Ratio
    Intake Opening: 5* BTDC
    Intake Closing: 39* ABDC
    Exhaust Opening: 49* BBDC
    Exhaust Closing: 5* BTDC

    E303 - 220*/220* - 282*/282* - .498"/.498" - .311"/.311" - 110* - 110*/110* - 2,500-5,500 RPM
    Overlap: 62 degrees.
    1.6 Rocker Ratio
    Intake Opening: 0* BTDC
    Intake Closing: 40* ABDC
    Exhaust Opening: 40* BBDC
    Exhaust Closing: 0* BTDC

    F303 - 226*/226* - 288*/288* - .512"/.512" - .320"/.320" - 114* - 109*/119* - 2,800-6,000 RPM
    Overlap: 60 degrees.
    1.6 Rocker Ratio
    Intake Opening: 4* BTDC
    Intake Closing: 42* ABDC
    Exhaust Opening: 52* BBDC
    Exhaust Closing: 6* BTDC

    X303 - 224*/224* - 286*/286* - .542"/.542" - .339"/.339" - 112* - 107*/117* - 3,500-6,500 RPM
    Overlap: 62 degrees.
    1.6 Rocker Ratio
    Intake Opening: 5* BTDC
    Intake Closing: 39* ABDC
    Exhaust Opening: 49* BBDC
    Exhaust Closing: 5* BTDC

    Z303 - 228*/228* - 290*/290* - .552"/.552" - .345"/.345" - 112* - 107*/117* - Up to 6,500
    Overlap: 66 degrees.
    1.6 Rocker Ratio
    Intake Opening: 7* BTDC
    Intake Closing: 41* ABDC
    Exhaust Opening: 51* BBDC
    Exhaust Closing: 3* BTDC

    Trickflow Camshafts

    TFS 1 - 221*/225* - 275*/279* - .499"/.510" - .312"/.319" - 112* - 108*/116* - 2,000-5,500 RPM
    Overlap: 53 degrees.
    1.6 Rocker Ratio
    Intake Opening: 3* BTDC
    Intake Closing: 38* ABDC
    Exhaust Opening: 49* BBDC
    Exhaust Closing: 4* BTDC

    Recommended Valve Springs:
    TFS-51400413 with 1.6 ratio rocker arms
    Recommended Valve Springs:
    TFS-31400414 with 1.7 ratio rocker arms

    TFS 2 - 224*/232* - 286*/294* - .542"/.563" - .339"/.352" - 112* - 107*/117* - 2,500-6,000 RPM
    Overlap: 66 degrees.
    1.6 Rocker Ratio
    Intake Opening: 5* BTDC
    Intake Closing: 39* ABDC
    Exhaust Opening: 53* BBDC
    Exhaust Closing: 1* BTDC

    Recommended Valve Springs:
    TFS-31400414 with 1.6 or 1.7 ratio rocker arms

    TFS 3 - 236*/248* - 298*/310* - .574"/.595" - .359"/.372" - 110* - 105*/115* - 3,200-6,800 RPM
    Overlap: 84 degrees.
    1.6 Rocker Ratio
    Intake Opening: 13* BTDC
    Intake Closing: 43* ABDC
    Exhaust Opening: 59* BBDC
    Exhaust Closing: 9* BTDC

    Recommended Valve Springs:
    TFS-31400414 with 1.6 ratio rocker arms

    Steeda Camshafts

    Steeda #18 - 220*/226* - .480"/.480" - 112* - 2,500-6,000 RPM (N/A or P/A)

    Steeda #19 - 220*/226* - 280*/286* - .480"/.480" - .300"/.300" - 115* - 2,500-6,000 RPM

    1.6 Roller Rockers
    Intake Opening: (1)* ATDC
    Intake Closing: 41* ABDC
    Exhaust Opening: 52* BBDC
    Exhaust Closing: (6)* BTDC

    Recommended Valve Springs:
    110lbs closed/312 lbs open

    Steeda #20 - 224*/230* - .544"/.544" - 112* - Unknown - Stroker or 351 and applied with 1.7 RR's)

    Crower Camshafts:

    Crower 15511 - 218*/224* - .468"/.486" - 114* - 2,200-5,500 RPM

    Competition Camshafts

    Comp XE270HR-12 - 218*/224* - 270*/276* - .544"/.544" - .320"/.320" - 112* - 108*/116* - 1,800-5,800 RPM
    Overlap: 49 degrees.
    1.7 Roller Rockers
    Valve Timing @ .006"
    Intake Opening: 27*
    Intake Closing: 63*
    Exhaust Opening: 74*
    Exhaust Closing: 22*

    Recommended Valve Springs:
    Competition 986-16

    Comp XE270HR-14 - 218*/224* - 270*/276* - .512"/.512" - .320"/.320" - 114* - 110*/118* - 1,800-5,800 RPM
    Overlap: 45 degrees.
    1.6 Roller Rockers
    Valve Timing @ .006" (.006" have higher degree numbers than .050" numbers)
    Intake Opening: 25*
    Intake Closing: 65*
    Exhaust Opening: 76*
    Exhaust Closing: 20*

    Comp XE274HR - 224*/232* - .555"/.565" - 112 - 108*/116*

    Lunati Camshafts

    Lunati 51014 - 218*/226* - 284*/292* - .500"/.510" - .300"/.306" - 112* - 108*/116* - 2,500-6,000 RPM
    Overlap: 64 degrees.
    1.6 Rocker Ratio
    Intake Opening: 1* BTDC
    Intake Closing: 37* ABDC
    Exhaust Opening: 49* BBDC
    Exhaust Closing: -3* ATDC

    Recommended Valve Springs:
    Part Number: 73100
    Cam Information

    Crane Camshafts

    Crane 2030 - 216*/220* - 270*/278* - .533"/.544" - .333"/.340" - 112* - 107*/117* - 2,000-5,500 RPM
    Overlap: 50 degrees.
    1.6 Rocker Ratio
    Intake Opening: 1* BTDC
    Intake Closing: 35* ABDC
    Exhaust Opening: 47* BBDC
    Exhaust Closing: (7)* BTDC

    Recommended Valve Springs:
    Part Number: 99841
    Valve Float: 6000 RPM

    Crane 2031 - 214*/220* - 276*/282* - .513"/.529" - .302"/.311" - 112* - 107*/117* - 2,000-5,500 RPM
    Overlap: 55 degrees.
    1.7 Rocker Ratio
    Intake Opening: 0* BTDC
    Intake Closing: 34* ABDC
    Exhaust Opening: 47* BBDC
    Exhaust Closing: (7)* BTDC

    Recommended Valve Springs:
    Part Number: 99841
    Valve Float: 6000 RPM

    Anderson Ford Motorsport Camshafts - No specs given are guaranteed 100% accurate.

    AFM B1 - 220*/222* - .490"/.530" - 110* -

    AFM B2 - 220*/226* - .529"/.544" - 112* - 108*/116*
    1.7 Roller Rocker

    AFM B3 - 218*/226* - .542"/.542"

    AFM B4 - 224*/232* - 286*/294* - .542"/.563" - .339"/.352" - 112* - 107*/117* - 2,500-6,400 RPM
    Overlap: 66 degrees.
    1.6 Rocker Ratio
    Intake Opening: 5* BTDC
    Intake Closing: 39* ABDC
    Exhaust Opening: 53* BBDC
    Exhaust Closing: (1)* BTDC

    Recommended Valve Springs:
    10308-1 Springs and Retainer

    AFM B-21 - 218*/226* - 272*/280* - .542"/.542" - .320"/.320" - 112* - 108*/116*
    Overlap: 52 degrees.
    1.7 Rocker Ratio
    Intake Opening: 1* BTDC
    Intake Closing: 37* ABDC
    Exhaust Opening: 49* BBDC
    Exhaust Closing: -3* BTDC

    AFM B-25 - 218*/226* - 272*/280* - .544"/.544" - .320"/.320"- 112* - 108*/116*
    Overlap: 52 degrees.
    1.7 Rocker Ratio

    Recommended Valve Springs:
    130lbs seat - 350lbs open - maximum rpm of 6,200 RPM

    AFM B-31 - 218*/228* - 270*/280* - .544"/.544" - 112* - 108*/116*

    AFM B-41 - 228*/236* - .544"/.544" - 2,700-6,700 RPM

    AFM B-4R - 226*/234* - 294*/302* - .544"/.544" - 112* - 108*/116*- (Renegade Cam)

    AFM B451 - 232*/240* 299*/307* - .576"/.576" - .360"/.360" - 112* - 107*/117*
    1.6 Rocker Ratio
    Intake Opening: 9* BTDC
    Intake Closing: 43* ABDC
    Exhaust Opening: 57* BBDC
    Exhaust Closing: 3* ATDC

    AFM B-51 - 2,700-6,700 RPM intended for 351-408 with supercharger.

    AFM N2 - Unknown

    AFM N3 - 218*/226* - 280*/288* - .542"/.542" - .339"/.339" - 110* - 110*/110* - 2,500-6,000 RPM
    Overlap: 64 degrees.
    1.6 Rocker Ratio
    Intake Opening: (1)* ATDC
    Intake Closing: 39* ABDC
    Exhaust Opening: 43* BBDC
    Exhaust Closing: 3* ATDC

    Recommended Valve Spring:
    Part Number: 99838
    Valve Float: 6,000 RPM

    AFM N4 - 222*/230* - .512"/.512"

    AFM N6 - Unknown

    AFM N-21 - 219*/229* - .512"/.512" - 110* -

    AFM N-41 - 222*/232* - 278*/286* - .512"/.512" - .320"/.320" - 110* - 106*/114*
    Overlap: 62 degrees.
    1.6 Rocker Ratio
    Intake Opening: 1* BTDC
    Intake Closing: 41* ABDC
    Exhaust Opening: 45* BBDC
    Exhaust Closing: 5* BTDC

    AFM N-412 - 222*/230* - 276*/284* - .512"/.512" - .320"/.320" - 112* - 108*/116*

    Intake Opening: 3* BTDC
    Intake Closing: 39* ABDC
    Exhaust Opening: 51* BBDC
    Exhaust Closing: -1* BTDC

    AFM N-51P - 228*/238* - .499"/.497" - .312"/.311" - 110* - 106*/114*

    AFM N-51HR - 226*/234* - 293*/301* - .520"/.528" - .325"/.330" - 110* - 105*/115*
    Overlap: 77 degrees.
    1.6 Rocker Ratio
    Intake Opening: 8* BTDC
    Intake Closing: 38* ABDC
    Exhaust Opening: 52* BBDC
    Exhaust Closing: 2* BTDC

    AFM N-61 - 228*/236* - 280*/288* - .544"/.568" - 340"/355" - 108* - 106*/110*- 2,500-6,500 RPM

    AFM N-65 - 226*/234* - .568"/.568" - 110*
    1.6 Roller Rocker

    AFM N-71 - 232*/240* - .576"/.576" - 110* - 2,700-6,700 RPM

    AFM N-81 - 236*/244* - .568"/.576" - 110* - 2,700-6,600 RPM

    AFM N-91 - 240*/248* - .576"/.576" - 110* - 106*/114*
    1.6 Roller Rocker
    Intake Opening: 14* BTDC
    Intake Closing: 46* ABDC
    Exhaust Opening: 58* BBDC
    Exhaust Closing: 10* ATDC
    (Valve events not confirmed)

    AFM N-111 - 248*/258* - 315*/325* - .576"/.576" - .360"/.360" - 110* - 106*/114* - 2,800-7,000 RPM
    Overlap: 100 degrees.
    1.6 Rocker Ratio
    Intake Opening: 18* BTDC
    Intake Closing: 50* ABDC
    Exhaust Opening: 63* BBDC
    Exhaust Closing: 15* BTDC

    AFM N-112 -

    AFM N-113 - 270*/278* - 337*/345* - .576"/.576" - .360"/.360" - 104 - 108*/?
    1.6 Rocker Ratio
    Intake Opening: 31* BTDC
    Intake Closing: 59* ABDC
    Exhaust Opening: 71* BBDC
    Exhaust Closing: 27* BTDC

    Holley Kit Cam - 221*/223* - 276*/280* - .509"/.509" - .318"/.318" - 112* - 2,000-6,500 RPM
    Possible Lunati cam: LUN-51027LUN).
    1.6 Rocker Ratio
    Intake Opening: 3.5* BTDC
    Intake Closing: 37.5* ABDC
    Exhaust Opening: 48.5* BBDC
    Exhaust Closing: -5.5* ATDC

    Wolverine 1087 - 222*/232* - 299*/309* - .510"/.534" - .319"/.334" - 112* - 107*/117*
    Overlap: 80 degrees.
    1.6 Rocker Ratio
    Intake Opening: 4* BTDC
    Intake Closing: 38* ABDC
    Exhaust Opening: 53* BBDC
    Exhaust Closing: (-1)* ATDC

    New part number is Sealed Power ZCS1177R
    #2

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