Degreeing the cam is about more than turning a pair of adjustable cam gears. The process ensures that the camshaft centerline sits in the correct position relative to the crankshaft for your particular engine.
What you need
- Degree wheel: Mounts on the crank snout. A larger diameter gives higher reading accuracy.
- Dial indicator with a stand: The stand must attach firmly to the cylinder head. The tip needs to be parallel with the valve stem for accurate values.
- Piston stop: Needed to find exact top dead center (TDC) with the degree wheel.
- Pointer: A simple coat hanger or welding wire fixed to the block, aimed at the graduations on the degree wheel.
- Cam card: Supplied with every camshaft, listing all the specifications: duration, lift, lobe centerline, lobe separation angle and more.
Step 1: Find top dead center
Mount the degree wheel on the crank snout and the pointer against the block. Thread the piston stop into the cylinder. Rotate the crankshaft clockwise until the piston touches the stop and note the degree reading. Then rotate counterclockwise until the piston touches the stop again and note that reading too.
Exact TDC lies halfway between the two readings. Adjust the degree wheel or the pointer so it reads 0° with the piston at TDC.
Step 2: Set up the dial indicator
Mount the dial indicator so the tip rests directly on the valve spring retainer (not the rocker arm). It is critical that the indicator tip is parallel with the valve; that is the only way to get an accurate reading.
When degreeing, the valve lash must be fully closed. Always measure from the top of the retainer.
Step 3: Measure the valve events
Rotate the crankshaft slowly clockwise and note the degree readings at which the valve opens and closes. These should match your cam card. Common reference points are 1 mm of lift (or 0.050") for the opening and closing points.
Step 4: Calculate the centerline
With the opening and closing figures you can calculate the centerline of the cam lobe. Compare it with the specification on the cam card. If it is off, the cam gear needs adjusting.
Step 5: Adjust
With adjustable cam gears you can rotate the camshaft forward (advance) or backward (retard) relative to the crankshaft until the centerline is right. Repeat the measurement after every adjustment to confirm.
Tips
- Most turbocharged and highly tuned naturally aspirated engines respond well to small overlap adjustments even after correct degreeing. But degreeing the cam gives you the stable baseline that makes further tuning meaningful. Also read why degreeing is necessary.
- If the cylinder head or block has been resurfaced, the cam timing shifts. Degreeing the cam compensates for this.
- Write down all your readings. They are valuable reference points if you need to troubleshoot later.
Need help degreeing your cam, or have questions about your cam specs? Contact Meksta.
Also read about timing belt or timing chain and compression.