Degreeing a camshaft verifies that the cam is installed in the correct position relative to the crankshaft. Even cams marked "straight up" can be off by several degrees from the manufacturer. A few degrees of advance or retard shifts the power band significantly — degreeing it costs two hours and can be the difference between a good engine and a great one.
Tools required
- Degree wheel (at least 12" diameter — larger is more accurate)
- Dial indicator with magnetic base
- Piston stop (threaded into the spark plug hole)
- Stiff wire or light pointer for the degree wheel
- Cam card (spec sheet from the cam manufacturer)
- Socket and ratchet for rotating the engine
Step 1: Find true TDC
The timing mark on the harmonic balancer is NOT reliable for degreeing purposes — it can be off by several degrees. You must find true TDC (top dead center) using a piston stop.
- Thread a piston stop into the #1 spark plug hole. If you don't have a piston stop, drill a hole through an old spark plug and thread a bolt through it.
- Rotate the engine forward until the piston contacts the stop. Read the degree wheel and mark this number (e.g. 25° BTDC).
- Rotate the engine BACKWARD until the piston contacts the stop on the other side. Read the degree wheel (e.g. 25° ATDC if your timing marks are symmetric).
- True TDC is exactly halfway between these two numbers. Adjust your degree wheel pointer until the midpoint reads 0°.
- Remove the piston stop before proceeding.
Approach the stop slowly and by hand both times. Bumping it with a breaker bar loads the rod and gives a reading a degree or two off, which defeats the whole point of the exercise.
Step 2: Set up the dial indicator
Mount the dial indicator so the plunger contacts the top of an intake lifter on cylinder #1, perpendicular to the lifter travel. The lifter must be in the lifter bore (not floating) and the pushrod must be removed, or the indicator must sit on the lifter directly.
Any angle between the plunger and the direction of lifter travel makes the indicator read low by the cosine of that angle. Get it square.
Step 3: Find maximum lift
Rotate the engine slowly and watch the dial indicator. Find the point where the indicator reads maximum — this is maximum cam lobe lift, the nose of the lobe. At this point, record the degree wheel reading. This reading, measured in degrees ATDC, is your intake centerline.
Because the lobe nose is nearly flat, reading the exact peak is imprecise. The more repeatable method is to find the two crank positions at a fixed lift either side of peak (0.050" down from max is common) and take the midpoint — that is the true centerline.
Step 4: Compare to the cam card
The cam card specifies the intake centerline (ICL). Compare your measured ICL to the specified ICL:
| Your reading vs. cam card | Meaning | Effect |
|---|---|---|
| Reading = cam card ICL | Cam installed exactly as ground | Power band as designed |
| Reading is LESS than cam card ICL | Cam is ADVANCED (shifted earlier) | More low-end torque, power band moves down in RPM |
| Reading is MORE than cam card ICL | Cam is RETARDED (shifted later) | More top-end power, power band moves up in RPM, may hurt idle quality |
Step 5: Adjust with offset keys or an adjustable timing set
Most cam sprockets use a Woodruff key to lock the sprocket to the cam. Offset Woodruff keys allow 2° of advance or retard adjustment. Adjustable timing sets, with multiple keyway positions, allow 4° or more in 2° increments. Repeat the degreeing process after any adjustment to verify.