The
purpose of degreeing a camshaft is to ensure that it is phased correctly with
the crankshaft. Some factors that may cause improper positioning are:
1. Cam or crank gear marked incorrectly
2. Incorrectly machined cam or crank gear keyways
3. Misindexed cam keyway or dowel pin
4. Improper machining of camshaft or crankshaft
5.Accumulation of machine tolerances
The
important factor to remember is that camshaft position pr phasing to the engine
is extremely important for the engine to operate at maximum efficiency.
Equipment
needed to properly “degree” in a camshaft. They are available at Franklin Cams
and are as follows:
1. Degreeing wheel
2. A rigid pointer that can be attached to the block
3. A dial indicator to accurately measure cam lift
NOTE:
Refer to your spec card for maximum lift and check your dial indicator to be
sure it has sufficient range to measure the full cam lift.
4.
Either a magnetic or attachable base to affix the dial indicator
5. A top Dead Centre stop
6. A solid lifter to fit your motor. Motors that have non adjustable rocker
arms will also require an adjustable pushrod that accommodates that motor
7. A means to attach the degree wheel to the crankshaft
THE
INTAKE CENTRELINE METHOD
There are several accepted ways to degree a camshaft. At Franklin Cams, we feel
the intake centreline method is the easiest and most accurate. This method of
cam degreeing is very practical and indifferent to design characteristics. It
simply involves positioning the centre, or point of maximum lift, of the #1
intake lobe with top dead centre of the #1 piston. The intake centreline method
still requires accuracy to be correct, but it is somewhat more forgiving. Once
you have degreeed a camshaft using this method, you will be surprised at its
ease. We also recommend positioning the dial indicator on the #1 intake
retainer because lift measurements will include and deflection that may occur
in the pushrod and rocker arm. This makes the degreeing process as accurate as
possible in relation to what actually goes on inside the engine.
TIME TO
GO TO WORK
Step 1:
The camshaft and timing set have been installed. Make sure that the timing
marks on both the cam gear and crank gear are aligned properly per the cam
installation instructions. Use chalk or similar marker to better define the
marks.
Step 2:
For
example, we have our cam card and it suggests we install the cam on 106 degree
intake centreline. Install all the rocker arms and pushrods in the motor as
normal. On #1 intake lobe, install the solid lifter in place of the hydraulic
lifter. If a solid lifter or roller cam is being checked, use that respective
lifter. Adjust the #1 intake lash to exactly zero. Do not pre-load the lifter.
Next, adjust the #1 exhaust last to zero. You should be able to turn both
pushrods with your fingers easily.
Step 3:
Attach
the pointer to the block. Many people will make a pointer out of some sort of
rigid, yet manageable wire. A stiff coat hanger wire works well.
Step 4:
Attach
the degree wheel to the balancer and install the assembly on the crankshaft.
There are several ways to attach wheel to the crankshaft. In our example, the
degree wheel is mounted to the balancer. The crank may be rotated from either
the front or from the flywheel end. Obviously, if the engine is in the car, you
must rotate from the front. Remember, the greater the leverage, the smoother
the crank rotation, thus more accuracy. NEVER use the starter to turn the
engine while degreeing the cam.
Step 5:
Before
installing the piston stop, rotate the crankshaft to get the #1 piston in
approximate T.D.C position with both the intake and exhaust valves closed. This
can be a rough guess, but it can save you from making a mistake later. Adjust
your pointer to zero or T.D.C on the degree wheel.
Step 6:
Turn
the crankshaft opposite the motor rotation approximately 15-20 degrees. This
will lower the position enough to allow the T.D.C. stop to be installed in the
spark plug hole. Screw in the piston stop until it touches the piston. Continue
to turn the engine in the same direction until the piston comes back up and
touches the piston stop. Mark the degree wheel with a pen or pencil on the
number the pointer is on. Turn the engine in the other direction, same as motor
rotation, until the piston comes back up and touches the piston stop. Make a
mark on the number the pointer is on.
Step 7:
Remove
the piston stop after marking the two points on your degree wheel. Rotate the
crankshaft to the midpoint of the two marks. This point is T.D.C. for cylinder
#1. Without rotating the crankshaft, adjust the degree wheel to read 0 degrees
at the pointer. You are now ready to locate the intake lobe centreline relative
to T.D.C. If you are not absolutely sure that your 0 degree mark is set at
T.D.C, repeat this procedure. This step by step is critical to proper cam
alignment.
Step 8:
Attach
the dial indicator to the dial indicator mount. Position the dial indicator
mount so the tip will contact the retainer of the 31 intake valve. It is
important that the indicator plunger be parallel to the valve stem. Any
variance in the angle of the indicator will introduce geometric errors into the
lift readings.
Step 9:
Rotate
the engine in the normal direction of crankshaft rotation until you reach
maximum lift. The dial indicator will change direction at the point of maximum
lift. At this point, set the dial to zero.
Step 10:
Back
the engine up (opposite normal rotation) until the indicator reads .100”. Turn
the engine back in the normal direction of rotation until the dial indicator
reads .050” before maximum lift. Record the degree wheel reading.
Step 11:
Continue
to rotate the motor over in its normal direction of rotation until the
indicator goes past zero to .050” on the closing side of maximum lift. Again,
record the degree wheel reading.
Step 12:
Add
the 2 numbers together and divide by 2. That number will be the location if
maximum lift of the intake lobe in relation to at the crank and piston. This is
the intake centreline. For example: The first degree wheel reading was 96
degrees. The second reading was 116 degrees. These 2 numbers (96+116) added
together will be 212. 212 divided by 2 will equal 106. Your actual intake
centreline is 106 degrees. Refer to your cam spec card and we see that the
recommended intake centreline for your camshaft is 106 degrees. Everything is
where it should be.
In the
event that your camshaft did not degree in as per manufacturers specs, it will
be necessary to either advance (move the cam ahead) or retard (move the cam
back) the cam to meet suggested intake centreline. Depending on the motor
application, there are several different suggested methods for advancing or
retarding the camshaft.
One
common method is by use of a crank gear with multiple keyways each one being at
a slightly different relationship to the gear teeth. A second method is to use
offset bushings that fit on the cam pin and in the cam gear. The offset will
advance or retard the cam depending on how the bushing is placed on the cam
pin. Another method is by offset keys that fit into the crank gear keyway. A
more elaborate system uses an adjustable timing gear. Contact Franklin Cams or
your local Franklin Cams dealer for the method best suited to your application.
NOTE:
When
degreeing a cam, remember to look at the degree wheel as a full 360 degrees no
matter how the degree wheel you’re using is marked. Many degree wheels are
marked. Many degree wheels are marked in 90 degree or 180 degree increments. On
wheels that are marked in 90 degree increments, keep in mind that you must
continue to count the number of degrees on past 90 degrees. Be sure all
readings are taken from Top Dead Centre.
Keep in
mind that to advance the cam, you must lower the intake centreline. For
example, if your cam has a lobe separation of 110 degrees, the cam is “straight
up” when the intake centreline is 110 degrees. Moving the centreline to 106
degrees advances the cam 4 degrees. If we change the centreline to 112 degrees,
this would be 2 degrees retarded.
We at
Franklin Cams hope that these instructions will be helpful in making your
camshaft installation and degreeing a successful experience.