Tech Tips

          Degreeing Your Camshaft

The basic tools required are:

1. A degree wheel  

2. A stable pointer that can be conveniently mounted to the engine.

3. A dial indicator with at least a half inch of travel in .001" increments. A rigid stand that mounts to the engine or with a magnetic base to hold the dial indicator will also be required.

4. A positive stop device to locate T.D.C. 


Determining exactly where Top Dead Center is can be tricky. The problem in finding the true T.D.C. of the piston's travel is that the piston dwells at T.D.C. for several degrees of crankshaft rotation. You must use a device to stop the piston in the same position on either side of T.D.C. and take readings from the degree wheel.

You will then split the difference in these readings and move the pointer this amount, making it the true T.D.C. point. Begin the procedure by first mounting the degree wheel on the end of the crankshaft securely, and rotating the engine to approximately T.D.C. Mount the pointer and line it up at zero on the degree wheel. Now rotate the engine to move the piston down into the cylinder. Install your positive stop device into the spark plug hole and extend the bolt. Now hand turn the engine (do not use the starter motor or you will put a hole through the piston), rotating until the piston comes up and stops against the bolt. Look at the degree wheel and write down the number of degrees shown by the pointer.

Hand turn the engine in the opposite direction until the piston comes up and stops on the bolt again. Go back to the degree wheel and write down the degrees it now reads. Add these two readings together and divide the answer by two. Now either move your pointer by this many degrees, or carefully loosen the degree wheel (without disturbing the position of the crankshaft) and move the wheel this required amount. Retighten the bolts, and rotate the engine again making sure that the readings on each side of T.D.C. are equal degrees away from zero. If they are, the zero on the degree wheel will now be the true T.D.C. point. Remove the positive stop device from the spark plug hole, as this procedure is complete.

  1. The dial indicator and stand must be attached securely to the engine. Any deflection could cause an error in your readings. Using the number one cylinder as a starting point, hand rotate the engine in a normal direction (clockwise, when standing in front of the engine) until the intake valve is at the highest point and zero the dial.

  2. Hand rotate the engine back till it passes the .050 mark then bring it forward till it is at the .050 mark and stop. Take a reading on the wheel.

  3. As you continue to rotate the engine, the reading on the dial indicator will rise up to the maximum lobe lift. The lifter is now on the top of the lobe, Continue the rotation and the lifter will start down the closing side of the lobe. Carefully watch the dial indicator as the numbers descend. When the indicator descends back to the .050" reading, stop, take a reading from the degree wheel and write it down.

  4. You now have the two important readings from the degree wheel, both taken when the dial indicator read .050".  Add the two numbers together and divide by two. This will give you your lobe center.
    The camshaft specification card provides much information, but the numbers you are most interested in for the degreeing of the cam are the lobe centers.


  5. You can follow exactly the same procedure on the exhaust lobe to determine its center and compare these readings to those on the specification card. If you also check the exhaust lobe you will have two points of reference (intake center, and the exhaust center) to go by. Remember, if you are plus or minus one degree of these readings, your cam is in the correct location and will be synchronized to the crankshaft's rotation.

 
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