how to read a cam spec card


Staff member
here is three typical cam spec cards
keep in mind cam spec cards give you the intended valve spring load rate,seat diam. specifications and clearances
BTW if your running a flat tappet cam INSIST ON A P55 core, to have it ground on as they are far more durable than the cheaper cores ... vl=2&prt=5

generally its best to purchase all the listed components in a cam installation kit (cam, lifters,valve springs, etc. ) from a single manufacturer as mixing parts, sources or brands,
allows the cam manufacturer to void the warranty, even if the parts in the kit they sell are either identical or inferior to,
the individually purchased components you individually sourced. keep in mind most manufacturers will have tested parts compatibility ,
so they are reasonably sure the components they sell in the kit will work, that can,t be always assumed,
with randomly matched parts even if those parts are good quality.
If your ordering any cam, be very sure you explain what year block and what cylinder heads will be used as there are differences in the cams. between early and later SBC, block s and the cams they require,and on big blocks theres similar issues, a mark VI cam is different from a MARK IV cam


most manufacturers IDENTIFY OR mark cams under the timing gear mount surface ... index.html ... ePages.pdf


this cam will typically be referred to by hotrodders as a 230/238 dur, 539/558 lift 112 LSA cam, but the advertised duration is 292/300 degrees


Part Number: 119661 Grind Number: HR-230/359-2S-12.90 IG
Engine Identification:
Start Yr. End Yr. Make Cyl Description
Engine Size Configuration
262-400 C.I. V

Valve Setting: Intake .000 Exhaust .000 HOT

Lift: Intake @Cam 359 @Valve 539 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 372 @Valve 558
Rocker Arm Ratio 1.50

Cam Timing: TAPPET @.004
Lift: Opens Closes ADV Duration
Intake 35.0 BTDC 77.0 ABDC 292 °
Exhaust 83.0 BBDC 37.0 ATDC 300 °

Spring Requirements: Triple Dual Outer Inner
Part Number 99838
Loads Closed 112 LBS @ 1.650 or 1 21/32
Open 327 LBS @ 1.120
Recommended RPM range with matching components
Minimum RPM 2600
Maximum RPM 6600
Valve Float 7000

Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 8.0 BTDC 42.0 ABDC 107 230 °
Exhaust 56.0 BBDC 2.0 ATDC 117 238 °

this chart comes in vary handy at times






when your reading a cam spec card, you'll want too keep in mind theres 720 degrees in a cycle and the cam turns at 1/2 the speed of the crank so the piston reaches TDC twice in one complete rotation of the cam, plus cam cards generally start with the exhaust valve opening not the intake valve as most of us might assume



this cam will typically be refered to by hotrodders as a 248/254 dur, 504/528 lift ,112 LSA cam, but the advertized dur is 282/292, obviously addvertized duration has little relation to true effective durration

look closely and youll usually see the lift at the cam, lift at the valve, the lobe seperation angle and the durration at .050 lift

this cam will typically be referred to by hotrodders as a 240/248 dur, but the advertised duration is 268/277 degrees, again the duration at .050 lift makes some sence but the advertised duration is all but meaningless

terms ... 10&go.y=12

Ed Curtis ( @
Buddy Rawls ( @
Jay Allen ( @

Camshaft Term Glossary

Degrees after bottom dead center.

Degrees after top dead center.

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.

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

Degrees before bottom dead center.

Degrees before top dead center.

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.

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."

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.

The actual shape of the cam lobe.

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.

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.

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)

See "Improved Stock Cams".

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.

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.

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.

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.

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

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

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

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".

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.

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.

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.

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.

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.

This is the clearance between the base circle of the camshaft lobe and the camshaft follower or tappet.

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.

The amount of travel the cam lobe has across the lifter face. Lifter diameter determines flank velocity.

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).

The distance measured in degrees between the centerline of the intake lobe and the centerline of the exhaust lobe in the same cylinder.

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.

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.

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".

Gas nitrating 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 nitrating 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 nitrating was originally conceived where sliding motion between two parts takes place repeatedly so is therefore directly applicable to solving camshaft wear problems.

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.

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

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

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.

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.

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

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.

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.

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

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).

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.


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 revving.
- Initially gives slower throttle response.
- Increases idle quality and create more vacuum.
- Increases piston to valve clearance.
- Reacts better for fuel injected engines.*

* Fuel Injected cars typically (not always) can take a wider LSA because they do not need the increased overlap period that aids in better air/fuel mixing. Just as well, most fuel injected cars need extra vacuum, which is a result, as shown above, as one decreases overlap or goes with a wider LSA.

You will also see that blower camshafts have wider LSA built in to the camshafts. Think about it, the increase of air from the blower will push out the extra air out of the exhaust if the overlap is too much. So you want a wider lobe separation angle, which decreases overlap of the valves.

So if you think about it, the wider (farther) the camshaft lobe peaks are from each other, the period both valves are open at the same time decreases. The tighter (closer) the camshaft lobe peaks are to each other, the period both valves are open at the same time increases.




you may find cross checking the figures against the CROWER charts useful
while not exact, simply because lobe acceleration rates differ,between manufacturers and flat tappet vs roller lobe designs, adding about 17 degrees to each cam lobe ramp to get the seat duration from the .050 lift value will frequently get you close to seat duration
its listed as a 230.8 @ .050 lift and 264 advertised
SO 17+230.8+17=264.8


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Staff member
YOU can,t expect to make even a wild guess as to which cam will be the best match to your engine combo, without thinking thru the whole list of components and how they will work as a matched complimentary group,what are all the other parts those cams will be matched with????
giving just the cam specs by them selfs is about as useful , without the application it will be used with,as asking if a pitch fork or a rake will work best....with out the context of what your trying to accomplish or what your dealing with, but as a general rule
roller cams USUALLY out perform similar flat tappet designs, and solid lifter designs USUALLY out perform similar hydraulic roller tappet designs,
READ THE LINKED INFO, and you'll LEARN A GREAT DEAL...STOP GUESSING, and understand how and why things interact, and youll be far ahead of the average guy



for those that don,t know you have options on the cams you order, that are not limited to the catalog options, alone, but be aware it can get rather expensive, and its not unusually for special order cams to take a month or two to arrive.
generally you can select what you need and its a listed option, yes you might want to change an existing cam, by ordering it on a tighter or wider LSA, occasionally you might want a longer intake duration lobe, matched to a shorter duration exhaust, on a custom LSA, like with a turbo application





engle cams ... atalog.pdf

elgin cams ... by+Part+No.

herbert cams






If your confused by the terms, lets try this, using this cam and the spring it lists

once installed the valve spring max length is the installed height,

max lift is installed height minus .060 minus coil bind

if you used these valve springs
Crane Cams#271-99846-16
Single Valve Springs
Outside Diameter: 1.255"
Inside Diameter: .870
Seat Pressure: 125 LBS @ 1.800"
Open Pressure: 383 LBS @ 1.200
Coil Bind: 1.100"
Rate (LBS/IN.): 428
Max Lift: .640
Set of 16

coil bind is 1.100 so minus .060 from the installed height of 1.800,you get 1.160 max permissible lift, but the valve only forces the spring to compress to max valve lift which will be less than the 1.160, while the installed height of 1.800 minus the max permissible lift with that spring 1.800-1.160= .640 in this case the cam lobe lift on the lifter multiplied by the rocker ratio provides a .536 max spring compression, since you have a max usable lift clearance of .640 available with that spring at that installed height,in this case, the .536 lift the cam lobe provides,compresses the valve spring about .104 less than the max permissible lift so clearance will be fine and the valve lift will never reach the full theoretical valve spring compression or load rate listed, it will with the stated load rate of 428 lbs per inch of compression see a lower rate than the listed 383 lbs as .536 lift x 428 lbs per inch of compression= roughly 230 lbs

BTW Im sure the question would come up about swapping to a 1.6:1 ratio rocker, how will that effect the result above?
cams are listed with the stock in this case (SBC) 1.5:1 rocker ratio, in the case above that provides a .536 lift on the exhaust lobe which is a bit more than the listed .518 on the intake,valve, if we were to swap from the stock 1.5:1 ratio to a 1.6:1 ratio you simply divide that listed .536 by 15 then multiply by 16 and you'll find you'll see a change to a .571 lift, still under the .640 max lift

Re: cam install info
I think most experienced guys have two or three degree wheels for that very reason,
(that the larger size is tough to fit in an engine compartment on an installed engine)
read this link
I bought these


you FIRST disconnect the battery and use a ratchet to spin the engine slowly by hand , useing the damper bolt and a 5/8 socket after removing the spark plugs, chalking the wheels and putting the cars trans in neutral

ways to turn over the engine WITHOUT the starter

theres large bolts for your ballancer

theres crank sockets


Crankshaft Socket Tool For turning AND MOUNTING Degree Wheels



crank rotaters

flywheel turning tools

finding TDC

youll need a piston stop and degree wheel to be exact
but thats not 100% required unless you want it to work correctly???
use of a camshaft install handle generally reduces the chances of damaged cam bearings



btw you might want to verify this next time you degree in a cam, so that next time you use dyno simulation software you enter the data correctly,





theres a hugely popular myth that simply is wrong, if your using a dyno simulation software program, ...,
no you don,t reduce or subtract the lift of the cam lobe by the lash, clearance,
when calculating the valve lift of a solid lifter cam,
and you don,t subtract the lifter seat movement on a hydraulic cam,
as that is ALL absorbed or removed on the cam lobes feed ramp
the lifter still lift,s the valve to the full lift
measure the difference the edge of the lifter moves from the time the lifter is on the cams base circle to peak lift than set the lifter back on the base circle again and set the dial indicator to zero with a .0024 feeler gauge between the lifter and dial indicator, and re measure total lift.
nothing changes on that peak lift , its change is absorbed by the cam lobes feed ramp.
the valve lash is clearance it does NOT add or subtract from the lift , if you have a solid lift cam rated at lets say .520 lift with a 1.5 :1 ratio rocker, changing the lash clearance,will effect how it runs and when the valve comes off the valve seat by a degree or two ,but unless you add a good deal more than the .024 specified lash clearance or so thats listed, on the spec card, for lash clearance, it has ALMOST ZERO EFFECT on total lift, and a change to a 1.6:1 ratio will effectively increase the lift to .554

the lifter starts on the base circle, the lobe passing under the lifter causes the lifter and pushrod to move up away from the base circle too peak lobe lift, the rocker ratio increases that lift at the valve through the leverage it provides working through the pivot point on the ball or axle inside the rocker centered on the rocker stud,
heres your typical cam spec card this one happens to be the crane cam I selected for my corvette

heres the spec card from the t-buckets 406 sbc



if you were to graph in the lash slack the valve lift would start a degree or so later and end a degree or so earlier,
but the total lift would remain constant as the distance the lifter travel in the blocks lifter bore as the cam lobe rotates under it,
from the base circle to the peak lift remains consistent



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