Camshaft Degreeing Procedure
The purpose of degreeing a camshaft is to ensure that it is phased correctly with the crankshaft. Some factors that may cause improper phasing are:
- Camshaft or crankshaft gear marked incorrectly
- Incorrectly machined cam or crank gear keyways
- Misindexed cam keyway or dowel pin
- Improper machining of camshaft or crankshaft
- Accumulation of machine tolerances
The important factor to remember is that correct camshaft phasing is critical for efficient engine operation. COMP Cams® offers all the equipment needed to properly degree in a camshaft, which includes the following:
- Degree wheel (COMP Cams® Part #4790)
- Rigid pointer that can be attached to the engine block (COMP Cams® Part #4794)
- Dial indicator with enough range to measure full cam lift (COMP Cams® Part #4909)
- Magnetic or attachable base to affix the dial indicator (COMP Cams® Part #4907)
- Top dead center stop (COMP Cams® Part #4795)
- A means to attach the degree wheel to the crankshaft. COMP Cams® Pro Crankshaft Socket (Part #4798) works well for this purpose, as it provides a convenient means of rotating the engine in addition to firmly anchoring the degree wheel in place.
Also required in order to degree your new COMP Cams® 4.6-liter camshafts are a 1” wrench and solid valve adjuster (lifter).
Intake Centerline Method
There are several accepted ways to degree a camshaft. COMP Cams® suggests the intake centerline method as the easiest and most accurate. This method of cam degreeing is very practical and indifferent to engine design characteristics. It simply involves positioning the center, or point of maximum lift, of the #1 intake lobe with Top Dead Center (TDC) of the #1 piston. The intake centerline method still requires accuracy to be correct, but it is somewhat forgiving. Once you have degreed a camshaft using this method, you will be surprised at its ease.
Step 1: The camshafts and timing chains have been installed. Make sure that the timing marks on both the cam gear and crank gear are aligned properly with the copper coated timing chain links as per the camshaft installation instructions.
Step 2: Position the #1 piston at Top Dead Center (TDC). Attach the degree wheel to the balancer or crank socket, and install the assembly on the crankshaft. 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, and the more accurately you can rotate the crankshaft. Install degree wheel and pointer, and set the pointer to zero on the degree wheel. Note: Never use the starter to turn the engine while degreeing a cam.
Step 3: Rotate the crankshaft opposite the engine rotation direction about 15-20 degrees. This will lower the piston enough to permit the installation of the piston stop in the #1 spark plug hole. Rotate the crankshaft clockwise until the piston hits the stop, and record the number indicated on the degree wheel. Next, rotate the crankshaft counterclockwise until the piston hits the stop from the other direction, and again record the number on the degree wheel.
Step 4: Remove the piston stop after marking the two points on the degree wheel. Rotate the crankshaft to the midpoint of the two marks (this is determined by adding the two points on the degree wheel together, then dividing by 2). This point is TDC 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 centerline relative to TDC. If you are not absolutely sure that your zero degree mark is set at TDC, repeat this procedure. This step is critical to proper camshaft alignment.
Step 5: Attach the dial indicator to the dial indicator mount. Position the dial indicator mount so the tip of the dial indicator extension/plunger will contact the retainer of the 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 6: Rotate the crankshaft clockwise until the camshaft reaches maximum intake lift. At this point, the dial indicator will begin to change direction at the point of maximum lift. At this point, set the dial to zero.
Step 7: Rotate the crankshaft counterclockwise until the dial indicator reads .100”. Next, turn the engine forward in the normal direction of rotation until the dial indicator reads .050” before maximum lift. Record the degree wheel reading.
Step 8: Continue to rotate the engine 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 9: Add the two numbers together and divide by 2. The resulting number will be the location of maximum lift of the intake lobe in relation to the crank and piston. This is the intake centerline. For example: The first degree wheel reading was 100 degrees. The second reading was 120 degrees. These two numbers (100 120) added together will be 220. 220 divided by 2 will equal 110. Your actual intake centerline is 110 degrees.
Verify that your measured intake centerline matches that listed on your camshaft specification card.
Step 10: Repeat the degreeing process on the opposite cylinder bank, this time using the number 6 intake valve to check the intake centerline. Note that it is not necessary to reestablish TDC in order to verify the #6 intake centerline.
In the event that your camshaft did not degree in to the camshaft specification, it will be necessary to either advance (move the cam ahead) or retard (move the cam back) the camshaft to meet the suggested intake centerline. There a couple of degrees of advance/retard available by loosening the timing gears (lock the camshafts again before loosening the bolts!) and rotating the crankshaft until the pointer is positioned at the desired intake centerline reading. Refer back to step 9 if you do not remember how to determine that reading.
Note: When degreeing a cam, remember to look at the degree wheel as two 180 degree sides, no matter how the degree wheel you are using is marked. Many degree wheels are marked in 90 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 Center.
Keep in mind that to advance the cam, you must lower the intake centerline. For example, if your camshaft set has a lobe separation of 114 degrees, moving the intake centerline to 110 degrees advances the cam 4 degrees. Conversely, moving the intake centerline to 116 degrees retards the camshaft 2 degrees.