Degree a Camshaft


Copyright © 1996 by Quality Performance Products


   A  four-cycle engine’s components work together in a very precise  relationship with each other.  For example: crankshaft to a connecting  rod; crankshaft / connecting rod to a piston; valves to a camshaft.  One  of the most critical relationships in an engine is the camshaft to  piston / connecting rod / crankshaft timing.  This instruction manual  will show you how to find and adjust this relationship for the best  performance results.

The tools you will need are:
            1- Large degree wheel   12” to a 24" diameter  (larger is more accurate)
            1- Adjustable magnetic base with a 1 inch travel dial indicator .001 Division
            1 - Short length of wire to bend into a pointer  (Coat hanger or electric fence wire)
            1 - 1/4 x 2 x 6 Aluminum plate to make a pushrod guide

      The path of least resistance in degreeing  a camshaft is when the crankshaft / piston assembly is able to rotate  smoothly.  You can accomplish this with only the # 1 cylinder piston  with rings and connecting rod installed.  Having the crankshaft  disconnected from the transmission is helpful if performing this  procedure in the chassis.  Install the camshaft and the # 1 cylinder  lifters into the block with light oil on the bearings, lifters and  camshaft lobes.  Install the cam gear(s), idler gear(s), crankshaft  gear(s), etc. to line up the camshaft and crankshaft timing marks.   Mount the degree wheel centered on the nose of the crankshaft so it  clears all other engine components.  Rotate the crankshaft until the # 1  cylinder piston is very close to TDC (Top Dead Center).  Rotate the  degree wheel on the crankshaft nose until the TDC marking is near the  top in a position easy to read.  Snug tight the bolt holding the degree  wheel to the crankshaft.  Bend the pointer wire and fasten it to the  block.  Adjust the pointer wire so it points at the TDC mark on the  degree wheel.  When making measurements, calculating midpoints or  centerlines, always rotate the engine components in their normal  direction of rotation.  This will ensure that the measurements reflect  what the engine components are actually doing.

      To find an approximate piston TDC, set the dial indicator on top  of the block so the dial indicator plunger is perpendicular to the  piston top.  Make sure enough dial indicator plunger travel is remaining  for the piston to travel up slightly, but more importantly for the dial  indicator plunger to follow the piston down approximately 1/4 inch.  Using light thumb pressure on top of the piston to take up bearing  clearance, rotate the crankshaft forward in normal rotation.  Continue  rotation until the piston reaches the end of travel at the top of the  block.  Set the dial indicator needle to zero. Rotate the crankshaft  opposite normal rotation and then forward again to recheck your piston  TDC dial indicator reading.  Align the pointer so it points clearly and  squarely at the degree wheel TDC mark. This is the approximate TDC  setting.

      To find the exact TDC location, rotate the crankshaft in reverse  of normal rotation until the dial indicator drops about .200 inch of  travel.  Slowly and smoothly rotate the crankshaft in normal engine  rotation until the dial indicator reads .100 inch of piston travel  before TDC.  Record the degree wheel pointer reading.    Example:     15  BTDC (Before Top Dead Center)
Continue to rotate the crankshaft in normal rotation until the dial  indicator reads .100 inch of piston travel after TDC (the piston came up  to TDC and started back down).  Record the degree wheel pointer  reading.        Example:    25 ATDC (After Top Dead Center)
The exact point of piston TDC will be ½ of the distance between the two recorded points.  [ Example:  15  BTDC and 25 ATDC ]  To find this midpoint, add the distance between 15 BTDC and 25 ATDC. The distance between 15 BTDC  and TDC is 15 degrees. The distance between TDC and 25 ATDC is 25  degrees.    Example:    15 + 25 = 40    This is the number of crankshaft  degrees between the two recorded example points.  Dividing this number  by two (2) finds the midpoint.    Example:     40 / 2 = 20    To locate  this calculated point, rotate the crankshaft in reverse rotation past  your first recorded number. [  Example:  15  BTDC ]   Rotate the crankshaft in normal rotation to your first recorded point. [ Example: 15 BTDC  ]  Continue in normal rotation another 20 crankshaft degrees (½ of the  distance between the two example points).  The wire pointer will now  point at  5 ATDC on the degree wheel. This is the example’s true TDC.   Without rotating or moving the crankshaft, loosen up the bolt holding  the degree wheel and rotate the degree wheel until the wire pointer  points precisely at the TDC mark.  Retighten the bolt holding the degree  wheel to the crankshaft.  As an option, realign the pointer to point  precisely at the degree wheel TDC mark. Either method is OK; use  whichever is easier.  Remember to view the pointer directly in-line   with the crankshaft to avoid parallax error.

      Repeat the TDC operation to confirm the accuracy of your  measurements.  Accuracy counts, so be sure to take careful measurements  and smoothly rotate the crankshaft to get exact dial indicator  readings.  If you overshoot your intended dial indicator reading, back  up and carefully approach the numbers again.  The numbers given here are  only examples. Your recorded numbers will be different, but the math  operations work the same way.

      The next step in this process is the camshaft timing.  What you  want to find is the precise midpoint or centerline of the # 1 cylinder  intake lobe and where this centerline is in relationship to the  crankshaft and piston TDC.  To do this, you need a procedure to measure  camshaft lobe lift.  The following pushrod guide fabrication is used  primarily for inline engines, but can be used for others if the camshaft  lifters are inaccessible to the dial indicator.  If the lifter is  accessible, the dial indicator can be setup to read directly from the  lifter.  You will use the aluminum stock to make a pushrod guide, if  required.  Measure the pushrod diameter carefully and drill a hole .005  to .010 inch larger in one end of the aluminum plate. Install a pushrod  into the camshaft’s # 1 cylinder intake lifter location.  Find a bolt  hole in the block deck close to the pushrod and measure the distance  between the pushrod and the bolt hole. It is essential that you try to  place the pushrod as close as possible to the OEM location to simulate  how it would actually move.  Layout this measured distance on the  aluminum plate from the previously drilled pushrod hole. Accurately  drill a hole in the aluminum plate large enough to insert a bolt through  the plate into the block deck. Bolt the aluminum plate pushrod guide  plate to the block with the pushrod installed in the camshaft’s # 1  cylinder intake lifter.  Make sure the pushrod is free to move up and  down in the aluminum plate without binding or wobbling.  Adjust the  pushrod hole diameter if necessary to eliminate binding.  Install the  dial indicator with the indicator plunger parallel with and straight  into the center of the pushrod end. Carefully align the dial indicator  so the pushrod is perfectly in line and free to rotate around the dial  indicator plunger. Alignment is critical to avoid cosine error.

      The next step will be measuring the camshaft lobe duration at .050  inch lifter rise on the opening ramp to .050 inch of lifter rise on the  closing ramp.  Rotate the crankshaft assembly in normal rotation to  find the camshaft base circle.  The base circle is the lowest point of  dial indicator travel measured from the pushrod travel.  Zero the dial  indicator and continue to rotate the crankshaft in normal rotation until  the dial indicator reads .050 inch of lifter rise.  This is the  camshaft’s intake lobe opening ramp.  Record the degree wheel pointer  reading.
Example:    20 BTDC      Monitoring the dial indicator revolution counter, continue normal  crankshaft rotation until the lifter has reached maximum lift.  The dial  indicator will display the total camshaft lift, record this reading to  compare with the camshaft specification sheet.  Resume crankshaft  rotation until the lifter is starting to drop.  This is the camshaft’s  intake lobe closing ramp. You want the camshaft closing reading at .050  inch before total lifter drop (the dial indicator will read .050 inch  before zero).  Record the degree wheel pointer reading.
Example:     40 ABDC  (After Bottom Dead Center).    The exact midpoint or centerline of the  intake camshaft lobe will be ½ of the distance between the two recorded  degree wheel readings. [  Example:   20 BTDC and 40 ABDC ]        To find this midpoint, add the distance between 20 BTDC and 40 ABDC.  The distance between 20 BTDC  and TDC is 20 degrees. The distance between TDC and BDC is 180 degrees  (the number of degrees in half a circle). The distance between BDC and  40 ABDC  is 40 degrees.  Add up all the distances in order:    Example:      20 +  180 + 40 = 240 degrees.  Record this reading to compare with the  camshaft specification sheet.  This is the number of crankshaft degrees  between the two recorded example points.  Dividing this number by two  (2) finds the midpoint.    Example:    240 / 2 = 120 degrees    To  locate this calculated point, rotate the crankshaft in normal rotation  to your first recorded point. [  Example:     20 BTDC ]     Continue in normal crankshaft rotation an additional 120 degrees (½  of the distance between the two example points).  This example will give  a crankshaft degree wheel pointer reading of 100 ATDC. This is the  camshaft’s # 1 cylinder intake lobe centerline in relationship to the  crankshaft and # 1 cylinder piston.

      You may have noticed that the checking height of the camshaft at  .050 lifter rise (from our example) is an industry standard for  comparing camshaft specifications. The distance between your previously  recorded measurements will give the camshaft lobe duration at .050  lifter rise.    [ Example:     20 + 180 + 40 = 240 degrees ]
The camshaft duration numbers always refer to degrees of crankshaft rotation.

     Repeat the camshaft centerline operation to confirm the accuracy of  your measurements.  Accuracy counts, so be sure to take careful  measurements and smoothly rotate the crankshaft to get exact dial  indicator readings.  If you overshoot your intended dial indicator  reading, back up and carefully approach the numbers again.  The numbers  given here are only examples. Your recorded numbers will be different,  but the math operations work the same way.

      You may need to correct the camshaft intake centerline from the  measured point to the specification given on your camshaft information  sheet. This can be accomplished by moving the camshaft with offset keys,  offset bushings, or by moving a tooth on the cam gear. The procedure  for calculating the camshaft timing change by moving a tooth on the  camshaft gear follows:
      1. Count the number of camshaft gear teeth     [ Example: 60 teeth ]
      2. Divide 360 (number of degrees in a circle) by the tooth count of the camshaft gear.
[ Example: 360 / 60 = 6 degrees ]  The result from the division will be  the number of degrees change in camshaft (not crankshaft) timing by  moving one tooth on the camshaft gear. An alternative option is to use a  multiple keyway crankshaft gear. Which choice works the best depends on  how far the camshaft timing needs to change.

      Moving the camshaft further ahead in normal camshaft rotation will  advance the camshaft (smaller ATDC number) and moving the camshaft  opposite normal camshaft rotation will retard the camshaft (larger ATDC  number) in relationship to the crankshaft.  If you move only the  camshaft gear, the change to the camshaft centerline timing will be  equal to 2 times the change in degrees of the camshaft gear.
Example:    If you advance the camshaft gear four (4) degrees, the  camshaft centerline timing will advance four (4) camshaft degrees or  eight (8) crankshaft degrees.  Remember the camshaft runs at ½  crankshaft speed and the timing diagrams are based on crankshaft  degrees.  If you move only the crankshaft gear, the change to the  camshaft centerline timing will be the change in degrees of the  crankshaft gear.  Example:    If you advance the crankshaft gear four  (4) degrees, the camshaft centerline timing to the crankshaft will  advance  four (4) degrees.

      Install the camshaft to the specifications (as close as possible)  given on your camshaft information sheet. Setting the camshaft intake  centerline to within one (1) degree accuracy will give the best engine  performance based on the information given when ordering a camshaft.  If  the camshaft timing is changed, follow this guideline: advancing the  camshaft centerline results in a powerband at a lower RPM, retarding the  camshaft centerline results in a powerband at a higher RPM.  Changing  the camshaft centerline will not generally increase the width of the  powerband in RPMs, but will shift the powerband up or down the RPM  scale.  If your application requires a different width powerband, you  may need a different camshaft grind.  Make sure you understand the  resulting effect before making any camshaft timing changes.

      The valve to piston clearance is an important issue when  installing a performance camshaft.  It is critical to piston and valve  train life that adequate clearance is provided.  A rule of thumb for  valve / piston clearance is .080 inch intake and .100 inch exhaust.   This should be checked by the individual assembling the engine.  While  the camshaft is opening the intake valve, the piston is approaching TDC  (start of an intake event).  The intake valve / piston clearance will  typically be the smallest after piston TDC.  Advancing the camshaft  intake lobe centerline will open the intake valve earlier, relative to  the piston position, and will advance the exhaust lobe centerline. The  lobe separation (number of camshaft degrees between intake and exhaust  centerlines) is a fixed parameter determined when the camshaft is  manufactured.  The exhaust valve is starting to close as the piston  approaches TDC (end of an exhaust event).  Exhaust valve/piston  clearance will typically be the smallest before piston TDC.

      This instruction manual is only a guideline. Its purpose is to  help the installer determine the relationship between camshaft and  crankshaft position.  For more information on the effects of camshaft  timing, valve lift and duration, lobe separation and overlap, rocker arm  ratios and valve lashes, consult publications available from camshaft  vendors. The installer accepts all responsibility for the camshaft  installation and accuracy of degreeing the camshaft centerline to the crankshaft.

Cylinder Honing

 Cylinder Honing

What is honing, how is it performed and  why is it important?  Honing is an abrasive process that improves the  surface finish, size, and roundness of a bored cylinder/sleeve. The  purpose is to create as close to an ideal surface as possible to mate  with ring faces.  Oil consumption and torque output are directly  affected by the finish on the cylinder walls.  Cost/benefit analysis  will help determine importance.
ost has two components.  Up front cost is the invoice received for the  work performed.  OEMs have analyzed costs associated with machining and  honing a bore/sleeve in the block. The benefits of high quality  standards are lower warranty cost, higher fuel economy and low oil  consumption. Hidden costs are the second piece of the puzzle.  A hidden  cost for an OEM is customer dissatisfaction with their product for which  is difficult to establish an actual dollar cost.  For the performance  market the up front costs are similar to the OEM’s with the additional  goal of increasing horsepower.  Hidden costs in the performance arena  are horsepower potential never realized and horsepower produced that is  consumed by parasitic losses.  Detonation, windage, blowby, ring  flutter, piston skirt scuffing, oil contamination and other effects will  be examined.  Hidden costs are real.  Perspective changes perceived  value.

Honing uses abrasive materials such as alumina, carborundum, silicon or  diamond powder bonded to a tool that is expanded and rotated in the  bored cylinder.  The abrasives remove material from the cylinder as the  tool is moved up and down in the cylinder.  This reciprocation creates  the familiar cross hatch pattern seen in cylinders.  The choice of the  abrasives, rpm, expansion pressure, cutting lubricant, reciprocation  speed and tool type affect the process and final finish achieved.  The  craft of honing is in understanding the process variables, controlling  them and achieving a finish compatible with the ring type and material  chosen for the application.  Honing is done to maximize ring seal,  piston ring and cylinder wall longevity.

Piston rings seal the gap between the piston and cylinder enabling  cylinder pressure to be converted into work.  The sides of the ring  groove in the piston and the sides of the ring seal because cylinder  pressure forces them together without significant movement between those  surfaces.  These surfaces are very smooth and flat and when pressed  together create a virtual metal to metal seal.  However, the ring face  and cylinder need to be sealed while the ring is moving at significant  speeds.  In an engine with a 5.0” stroke running 6,000 rpm, the average  piston speed is 83.33 ft/second or 56.83 mph. Peak speed at mid-stroke  is much, much faster.  The ring must seal very high peak cylinder  pressures (over 3000 PSI), maintain that seal while cylinder pressure  drops as the piston moves toward bottom dead center, survive the heat of  combustion (in excess of 5000 F.), withstand the surface friction of  those speeds, give a low friction ride back to top dead center and then  repeat.  Obviously, metal to metal contact between ring face and  cylinder would lead to catastrophic failure in several engine  revolutions.  Good rings mated to properly honed and sized cylinder  walls for those type rings and engine oil create a microscopic barrier  of oil captured between the ring face and the cylinder surface.  That  microns thick film of oil seals cylinder pressure, prevents metal to  metal contact, and transfers 20% of combustion heat from piston to ring  to cylinder wall and then into the cooling system.  It is the barrier  that separates success from disaster.

Maximum ring sealing is the goal of proper cylinder finishing and it is  critical for maximum power production.  Blowby is the result of  deficient ring seal.  Rule of thumb indicates that every 2% increase in  blowby costs 1% of horsepower due to lost combustion pressure.  However,  lost compression is only one factor in the equation. Another factor is  increased windage.  Blowby creates crankcase pressure which increases  windage.  Imagine your crankshaft and connecting rods whipping through  all the oil draining back into the pan and then add the extra combustion  gases leaking past the rings.  This mixture of oil and combustion gases  forms a “slurry” (like whipped cream) that surrounds and rotates with  the crankshaft.  The parasitic loss of power due to rotating this extra  mass is measurable.  A reduction in oil flow (the gases entrained in the  oil slurry are compressed and fed back into the oil system) and  subsequent loss of lubrication and oil cooling is an additional effect  of windage.  A portion of the compressed air in the oil will find the  path of least resistance to escape, usually in the rod and main bearing  oil circuit.  The loss of lubrication volume from entrained air  adversely impacts valve train components as well.  Once pressure leaks  past a part of the top ring, a cascade of effects occurs.  First the  ring is distorted and contact pressure between cylinder wall and ring  face oil film is increased in some areas while others areas are  reduced.  Second, the high speed sheet of hot combustion gases can  “wipe” away the oil film below the ring causing the ring to further lose  local sealing and heat transfer capability.  If severe enough,  combustion gases leakage can blow past the secondary and oil rings which  induces piston skirt scoring.  Combustion gases burning the oil film  around the oil rings creates “Coking,” a carbon residue that impairs oil  rings’ ability to uniformly distribute the oil film.  Third, if enough  ring face contact is lost the ring can flutter against the cylinder  wall.  The ring then loses cooling capability, becoming locally annealed  (softened) allowing even more leakage and increased wear on the piston  ring grooves.  Leakage can travel in both directions.  Combustion gases  into the crankcase as previously discussed and crankcase windage  pressure pushes the oil slurry up past the rings during the exhaust  stroke when the piston is traveling towards Top Dead Center.  Oil  contamination of the combustion chamber creates localized hot spots of  carbon increasing the possibility of detonation.  Detonation pressure  spikes are severe enough to damage rings and break ring lands on the  piston.  A false economy solution to blowby is to add more boost.

However, adding boost pressure compounds the problem of ring seal.   Increased combustion pressures increase bore distortion, oil film  contact pressures and heat transfer requirements all which lead to  increased leakage.  Typical boosted engines can experience leakage of  over 5%.   Lost pressure means lost potential horsepower.  These losses  quickly add up.  Losing 1% of 1000 hp to increased windage is 10 HP,  losing 5% to lost pressure is another 50 HP.  The penalty is a  diminishing return for bigger or higher efficiency turbochargers which  in turn creates a larger cycle of loss.  An 1/8 inch or less of ring  material separates the combustion event from the oil pan.  Thus ring  seal is critical in capturing the increased cylinder pressure generated  by improvements to camshafts, induction, combustion and exhaust  systems.  Unless manufacturing piston rings is a viable option, the only  part of the ring seal you can affect is the cylinder wall preparation.  

There are two major factors in cylinder preparation: size and surface  finish.  Size may sound simple but is as complicated as surface finish.   Size is relative to taper and out-of-round.   Taper can be categorized  three different ways.  Bell-mouthed taper is largest at one or both  ends. Barrel is with the bore largest in the middle.  Linear taper goes  from the smallest to the largest, one end to the other.

Out-of round bores can be described by levels of “order.”  A first order  bore is round and true without any distortion.  Second order distortion  is oval in nature, created by poor machine accuracy or heat transfer  while machining.  A third order distortion is defined by a triangular  shape, sometimes described as a lobe, and is caused by a combination of  second and fourth order distortions. Excessive tool pressure during the  boring procedure can cause lobes.  High stone pressure with honing tools  that are centered or supported by contact in the bore can also cause  lobes. These two scenarios cause localized distortion as the cutting or  honing edge pushes and moves areas in the bore with little backing or  support (the middle of the sleeve or cylinder).  Fourth order distortion  is a square or cloverleaf shape usually created by bolt hole location  and spacing.

Sizing a sleeve or cylinder has a number of issues to consider.  Is the  size determined by maximum or minimum measurements taken?  How are these  measurements taken?  How cylindrical (close to absolute round and size  over its entire length) is the bore?  At what temperature was it  measured? Distortions are difficult to accurately measure.  A bore gauge  located by three points and measuring across two points cannot  accurately measure a second order distortion, can’t detect a third order  distortion and will detect but not accurately measure a fourth order  distortion.  A tool rotated in the bore (dial indicator mounted on a  boring bar, for example) can measure second, third and fourth order out  of round.  A honing tool with more edges than the order of distortion  can help remove lobes left from a boring operation.  A four edged honing  tool removes a third order error and a five edged tool removes a fourth  order error, etc.  This is why super-abrasive tools have six or more  cutting edges.  The increase in edges allows for a decrease in  individual stone pressure and better centers the tool within a distorted  bore, both of which help produce a rounder finished bore.

Surface finishes are defined by Ra, Rk,  Rvk, and Rvp.  Very specific  finishes are required for adequate oil retention and ring seal in  internal combustion engines. Some definitions are needed here.  All  machining operations including grinding and honing leave tooling marks  in the material they are cutting.  Machine type, cutter geometry,  machining speeds and feed rates and material type affect the finish left  post machining. The average roughness of a machined surface is defined  as Ra.

Ra is measured in micro inches (one micro inch is one millionth of an  inch or .000001”).  A profilometer is required to measure Ra.  The  profilometer’s diamond stylus is moved across the surface to measure  distribution (size and quantity) of the peaks and valleys of the tooling  marks. However, Ra does not tell the complete story of the surface  profile.  Other values are needed to define the surface.  Rpk is the  average peak height; Rvk is the average valley depth; and Rk is the  average core roughness depth.  All of the R numbers combined create a  more comprehensive view of the surface.  A graph that plots all the R  values showing the extent of the load bearing surface is an  “Abbott-Firestone Curve.”  Plateau honing creates flattened peaks, or  plateaus, which increase the load bearing surface relative to Rk and  reduces Rpk (imagine the surface difference between a threaded and  smooth rod.)  Even more complicated, there is the concept of “lay.”  Lay  refers to the predominant direction in which tooling marks are found on  a machined surface. However, lay does not affect R values.  The cross  hatch pattern typical to most honed cylinders is a type of lay.

Cross hatch is important for ring seal and ring life and the required  angle is determined in part by the sleeve or block material.  In cast or  nodular iron cylinders a narrow cross hatch angle of less than 20  degrees will cause excessive ring rotation and resultant ring and piston  ring land wear. Worn ring lands allow blowby.  Conversely, too large of  a cross hatch angle, or more than 40 degrees, causes a loss of oil film  retention and thus sealing, and reduces ring rotation leading to  increased cylinder wall wear.  Nikasil and other plated bore surfaces  require a flatter cross hatch of 10 to 15 degrees.  Ring manufacturers  publish extensive data on recommended bore finishes for their products.   Following their advice is prudent unless there is sufficient evidence  that another finish is better suited to the specific application.

A true first order bore at specified surface finish, correct lay and at  precise size is incredibly difficult to achieve. Accurate machines with  rigid spindles, correct honing tools, cutting lubricants, combined with  operator skill and adequate measuring tools are all required to get  close.  However, despite using the best procedures and equipment, the  cylinder or sleeve bore changes when the engine is assembled and then  again when run under load.  Head bolt loading, sleeve counterbore  alignment in the top of block relative to the bottom of the block,  counterbore depth uniformity and flatness, uniformity of sleeve flange  height, block deck flatness and cylinder head flatness all affect  cylinder bore distortion when assembled.  Good block inspection and  re-machining as needed, quality sleeves and proper head bolt torque  procedures during assembly will help reduce distortion.  Of all the  possible distortions, out-of-round is more important than taper for ring  seal and ring life.  Better yet for sleeved blocks is honing the  sleeves while installed in the user’s block and clamped in place with  torque plates.

The stock block started out factory machined for accuracy, but by now  can have thousands of running hours and heat cycles. This is a seasoned  block.  A seasoned block has moved, shifted and distorted in all areas  from when factory machined.  In other words, it has been stress relieved  and stabilized by those thousands of hour of use.  Qualifying a  seasoned block, re-machining as needed, and then honing the sleeves in  place will provide the most distortion free method of preparing sleeves  for assembly.  By installing sleeves in the block, serializing and  clocking each sleeve to its position in the block and using a torque  plate, the sleeve will distort as it will be in the final assembly.   Honing sleeves in the block allows finish honing with minimum out of  round and taper.

Good block preparation, matching ring type to sleeve finish, round and  straight sleeves when installed and engine assembled, meticulous  cleaning and good assembly procedures will give you the best performance  for the money.  The tangible benefits realized are increased  horsepower, durability and consistency.  Now that is the best “Bang for  the Buck.”


By engineering definition, resistance against penetration.  For cams and lifters, hardness is directly related to resistance against wear.  A typical iron cam registers in mid- to high-40s on the Rockwell C scale (Rc).  Compatible lifters register five to ten points higher.  The smaller part, running hotter, must be harder to equalize wear between parts.

A number of heat-cycle processes to alter the surface hardness of a metal.  The temperature of the part is raised to to the critical temperature, held there for a specified time, then allowed to cool at a specified rate to nearly room temperature.  This heat cycle alters the crystal and grain structures of the metal, which affect its hardness.  Some processes also diffuse carbon or nitrogen atoms into iron surfaces.  All flat and roller tappets are heat treated.  Some iron cams (mostly British) are heat-treated after re-grinding, to regain surface hardness.  See: “CARBURIZING, CHILLED IRON LIFTER, FLAME HARDENING, HARDNESS, INDUCTION HARDENING, NITRIDING, and QUENCHING.”  

Performance camshaft materials used may require carburization. 4620, 8620, P-6 ,S7 are alloys used for cams. There are others. Carburization is used for materials which have a low carbon volume. You need carbon to harden. This is a process used by all cam manufacturers. Carburization is adding carbon to all exposed surfaces to a specific depth. Camshafts I have examined are normally surfaced treated .030 /.120 deep with a surface hardness of Rockwell "C" from 55-63. Very hard for durability  and  to withstand the line contact of the roller. Carburizing exceeds  nitriding for a performance camshaft especially for roller tappet use.

Gas nitriding is a surface heat treatment that leaves a hard case on the  surface of an iron cam.  The hard case is up to .010” deep and is  typically twice the hardness of the core material.  The process is  accomplished by placing the cam into a sealed chamber filled with ammonia gas, and heating it to approximately 950 degrees F (510 degrees  C).  At this temperature, a chemical reaction occurs between the ammonia  and iron of the cam to form ferrous nitride on the surface of the cam.   As the reaction progresses, ferrous nitride diffuses into the cam core  to a case depth of approximately .010”.  The nitriding process is done at relatively low heat (as heat treatments go), so the core material  loses no hardness.  Also, the chamber temperature is raised and lowered  slowly, so that the cam is not thermally shocked, which would create  internal strains.  Gas nitriding was originally intended for where  sliding motion between two parts occurs repeatedly, so it is therefore  directly applicable to solving camshaft wear problems.  Ferrous nitride  is a ceramic compound, which accounts for its hardness.  It also has  some lubricity when sliding against other parts. 
Straight testing cannot be performed by Rockwell "C" because the diamond needle and weight used to protrude the needle into the surface used to check hardness would pass through the nitrided surface. One hundred fifty grams are used to measure Rockwell "C" harness. Material which has been nitrided uses a similar method to measure hardness, but uses only 15 grams; hence the name "15N" superficial hardness testing. By using this process, the actually surface hardness is measured.

A process for the surface hardening of alloy steel. Induction hardening is one of the most widely employed to improve component durability. It  creates in the work-piece a tough core with tensile residual stresses  and a hard surface layer with compressive stress, which have proved to  be very effective in extending the component fatigue life and wear  resistance. The work-pieces are heated by means of an  alternating magnetic field to a temperature within or above the  transformation range followed by immediate quenching. The core of the  component remains unaffected by the treatment and its physical  properties are those of the bar from which it was machined. The  hardness of the case can be within the range 37/58 HRC.   Carbon and  alloy steels with an equivalent carbon content in the range 0.40/0.45%  are most suitable for this process.  The effectiveness of this treatment depends both on surface materials properties modification and on the  introduction of residual stress.  A source of high frequency electricity  is used to drive a large alternating current through a coil. The  passage of current through this coil generates a very intense and rapidly changing magnetic field in the space within the work coil.  The  work-piece to be heated is placed within this intense alternating  magnetic field where eddy currents are generated within the work-piece  and resistance leads to Joule heating of the metal.  By quenching this  heated layer in water, oil or a polymer based quench the surface layer  is altered to form a martensitic structure which is harder than the base  metal. 

The final stage in ferrous heat-treating processes is cooling the workpiece nearly to room temperature.  The rate of cooling affects the resulting microstructure in metals, and from that either hardness or toughness.  Quenching cools the fastest and generates the hardest surface.  The quenching liquid is often water for large parts, but must be oil for very small parts (like needle bearing rollers) to prevent them cracking from thermal shock.
A thermo-chemical surfacing process, whereby a nonmetallic, oil-absorptive coating (manganese phosphate) is applied to the outside surface of the camshaft except on the mains (journals).  The lubricity of this coating permits rapid break-in of cam lobes without scuffing.  (The Parker family developed this process in New Jersey in the 1920s.)   
A cam tappet/lifter made from high-quality iron alloy that is heat-treated during its casting.  Molten iron is poured into a honeycomb mold with a chilled steel plate at the bottom, to quench and so heat-treat the face of the lifter. The heating and quench process brings carbide nodules close to the surface for excellent durability. This type of tappet is compatible only with steel and hardface overlay cams. 

A cam follower made from a special high-quality iron alloy that is compatible with cast iron billet camshafts.  The entire cylindrical body of a hardenable iron lifter is hard, in contrast to a chilled iron lifter with only its base hardened.

A small amount of spherical crown ground on the faces of most nominally “flat” tappets, to prevent the edge of the tappet from riding off the edge of a tapered cam lobe.  The amount of crown is determined by the amount of lobe taper, both being set by the engine manufacturer.  Normal tappet wear occurs as a “donut” partway off-centered on the face.  Wear near the edge indicates a tappet with too little crown for that cam.  Loss of specified tappet crown indicates a worn cam.

The small amount by which one side of a flat-tappet lobe is larger than the other, even though both follow the same profile.  Cams carry taper left or taper right and zero to .003” taper, depending on the engine. The direction and amount of taper is measured best across the diameter of the base circle.  Hold the front of the cam to your left (as a cam-grinding machine does).  If the forward (left) side of the lobe is larger, that is taper-left (TL).  If the rearward (right) side of the lobe is larger, that is taper-right (TR).  All lobes should measure with the same amount of taper, but not necessarily the same direction.  TR pushes cams into the block, off the angled pressure from tappets.  Engines with TL, mixed tapers, or roller tappets (with no taper) require a cam thrust plate.  Lobe taper works with tappet crown and tappet bores offset from lobes bores to drive flat tappets into rotation.   See: “Tappet Crown, Tappet Rotation.” 

Flat tappets must rotate in their bores, to continually present a fresh part of their face against a rotating cam, and thus equalize and minimize wear.  In contrast, roller tappet bodies must NOT rotate at  all.  If the roller tappet body is allow to rotate,  the roller wheel edge will impact  the camlobe.  The can result in catastrophic damage to the engine.   Rotation is driven by offsetting  the lifter bore from the center of the lobe face, lobe taper in the same direction as lifter offset, and lifter crown to match lobe taper.  Before installing tappets, check that each lifter is free to rotate in its bore, and apply only engine oil (not sticky “cam lube’) on the sides of lifters.  If a flat tappet does not rotate sufficiently, or at all, that lifter and cam lobe will wear out prematurely, perhaps as soon as break-in.

A man-made motor oil additive essential for dry lubrication between camshafts and flat tappets, where extreme pressure squeezes away all the oil molecules.  ZDDP* circulates with oil in 800-1200 parts-per-million, until it is crushed within a cam-lifter interface and plates itself into the iron surfaces.  Progressive reduction in percentages of ZDDP in motor oil since 2001 is causing premature wear in many high-performance street cams.  (*Zinc dialkyl dithiophosphate.)