How to Degree a Cam: Degreeing Techniques
- When it comes to degreeing the camshaft, in essence what we're doing is measuring the valve events and then comparing them to the recommendations from the cam manufacturer.
We may then need to move or adjust the cam timing in order to align the measured valve events with the recommended valve events.
As with many aspects of engine building, there's more than one method of degreeing the camshaft and they aren't all created equal.
So we're going to discuss the options here.
One of the most common methods is the camshaft centreline method where we find a point either side of peak lift where the valve lift is equal.
This for example might be a point where the lift is 50 thou less than peak valve lift.
With this method, we're assuming that if we're looking at the same lift point on either side of peak lift, then the centreline of the cam should be exactly in the middle.
The problem with this method is that it assumes that the cam lobe is symmetrical which is seldom the case wtih modern cam profiles.
This can introduce an error in the actual cam timing that may be anywhere from one to two degrees through to five degrees or more, depending on the specific cam profile and that point that we've used for our measurement.
Another technique that's often used due to the fact it can be done very quickly, is to check the lift at top dead centre and adjust the cam timing until the value matches the manufacturer's cam card.
The problem with this technique is that we're only making one single measurement and this allows a lot of room for error.
For this reason, the technique that we prefer and the one that will be taught in this course is the technique of measuring the valve opening and closing events, typically either at 50 thou or on millimetre lift, depending on the cam manufacturer.
This offers the best accuracy and we have the ability to confirm our results at two points on the cam lobe.