Camshaft Timing

One question we are asked again and again is how to time in a camshaft. Whilst we do not recommend that this is attempted by a complete novice, we thought it pertinent to give a description of the process for those wishing to attempt fitting and timing a camshaft themselves.

The first point of note is the identification of the camshaft and more importantly of the LCA (Lobe Center Angle). Manufacturers will normally stamp some identification on the rear face of the camshaft and this will either specify an angle or give the grind number so that the angle can be further researched. As an example we will dial a camshaft in that has an LCA of 109 degrees. This 109 degrees refers to the maximum open position of the camshaft follower for No. 1 inlet valve relative to top dead center on the engine. If the LCA is 109 degrees as in this case, then the maximum lift on No.1 inlet should occur at 109 degrees after top dead center.

Before you begin the timing procedure, fit the camshaft, fit the bottom sprocket to the crankshaft, fit the timing chain and fit the top sprocket loosely to the camshaft with camshaft key way at approximately 9 O'Clock and the crankshaft key way at approximately 2 O'Clock and the locating dots on the top and bottom sprocket aligned together. If you forget to do this you will need to remove the protractor and restart the procedure from scratch.

  • Tools
  • Setting TDC
  • Timing The Cam

In order to begin the timing procedure you will need a few non standard tools:
a) A center mounted protractor.
Cam pointer
b) A firmly-mounted pointer
Dial test indicator
c) A DTI ( Dial test indicator) with a mounting bracket
Piston dead stop
d) A dead-stop for the piston crown
Modified front pullet bolt
e) A modified front pulley bolt to hold the protractor
f) A camshaft follower (sometimes called a lifter or tappet)

The first step in the process is to identify an absolutely accurate TDC (Top Dead Center) position. Do not trust the front pulley timing marks, although they are often fairly accurate the camshaft timing is critical and three degrees discrepancy on the crankshaft will make a huge difference to the way that the engine performs.

1) Mount the pointer and the protractor to the front of the engine.
2) Bolt the dead stop over the No.1 Piston (front right cylinder if viewed from the from of the engine)
3) Adjust the dead stop to hold the piston a few degrees from its top rest position.
4) Adjust the position of the protractor so that the TDC mark is aligned with the pointer:
Top dead centre
5) Rotate the engine backwards (without adjusting the dead stop) until the piston again comes in contact with the dead stop.
6) Read the figure off the protractor, it is 60 degrees in the picture below (it will be different on every engine depending on the position of the dead stop):
7) Now loosen the dead stop and rotate the engine backwards (anticlockwise) until the protractor reads half of the read figure (in this case 30 degrees):
30 ddegrees btdc
8) Now loosen the nut holding the protractor and move the protractor anticlockwise until TDC lines up with the pointer (should be a 30 degree rotation) and lock the protractor firmly in this position.
Top dead centre
9) We need to double check that the TDC is correct so we now rotate the engine backwards until the protractor reads 10 degrees BTDC. Adjust the dead stop to hit the top of the piston:
10 degrees btdc
10) Now rotate the engine backwards (anti clockwise) until the piston again hits the dead stop.
10 degrees btdc
11) If the two figures are equal on opposite sides of TDC as shown above then you have established an accurate TDC and checked that it is correct. If the two figures are not equal on either side of TDC then you need to go back to step 3 and start again.
12) Now loosen the dead stop off completely and rotate the engine backwards until the TDC marker is aligned with the pointer. Make a visual check that the dots on the top and bottom sprocket are approximately aligned. This is the position of TDC and on the correct stroke.
Okay, we have now established a good and accurate TDC reading and the protractor should not be moved again during the entire timing process. We can now begin to set the camshaft timing.

Now remove the dead stop from the block and attach the DTI to the block so that the rod is centered in the top of the follower in No.1 inlet slot:
Dial test indicator
1) Rotate the engine forwards (clockwise) through one complete rotation returning to TDC. Continuing to rotate the engine forwards until the protractor reads 100 degrees.It is important to rotate the engine forwards as the tension on the timing chain is maintained:
100 degrees
2) Set the pointer on the DTI to 0 on the moveable outer ring.
3) Slowly rotate the engine forwards and watch the DTI reading. The pointer should rise to a maximum and then begin to drop. When the needle returns to the 0 marker stop.
4) Read the protractor. In this instance it reached 106 degrees:
106 degrees
5) The crank has moved 6 degrees which in turn means that the camshaft has rotated 3 degrees. This means that the current camshaft timing is 103 degrees which is 6 degrees too far advanced from the 109 degrees we are looking for.
6) This particular timing chain set uses a multi key way bottom sprocket to adjust the timing (some others have four adjustable bolts on the top sprocket). We need to take the bottom sprocket off the crankshaft key way in order to move the key way but we also need to retain a reference point of for the two sprockets so at this point we rotate the crankshaft forwards until TDC is again at the pointer. At this point the two dots on the top and bottom sprocket should be aligned once more. Do not rotate the crankshaft or move the camshaft at this point.
Sprocket set
7) Now pull the bottom sprocket forward until it is released from the key way Rotate the sprocket until the -6 key way lines up with the crankshaft key (this will obviously be different if your initial timing reading was different from ours - use the figure from stage 5 above for your camshaft). Now push the bottom sprocket back onto the crankshaft key and re-fit the top sprocket to the camshaft with the two dots aligned again, you may need to rotate the camshaft slightly to get the top sprocket onto the camshaft key.
8) You have now returned to stage 1 of the camshaft timing process. Run through stages 1 to 5 once more. If you have calculated and observed correctly then you should see a reading of 118 degrees on the protractor:
118 degrees
9) The picture above shows 118 degrees which means that the protractor has moved 18 degrees and therefore the camshaft has moved 9 degrees, the camshaft timing is therefore 109 degrees after TDC which is correct for this camshaft and the procedure is complete. If you did not manage to get the figures to match your camshafts timing figure then you will need to return to step 1 and start again.
It is pertinent to point out at this juncture that this can be a lengthy procedure, as long as you follow the steps accurately it should, eventually, produce an accurately timed camshaft and therefore a healthy engine. Do not be tempted to 'make do' with something close .. it is not worth it! We would also recommend at least one check procedure of the final timing figure to be absolutely sure you have it correct.