Lesson3/Learning Event 2
Now let's see how this advance mechanism works. With the engine running at an idle speed, the
springs hold the weights in their retarded (no advance) position. As the engine speeds up, the
weights try to fly outward; but, to do this, they must first overcome spring tension, which they will
do once the engine is running fast enough. As the engine speeds up, the weights gradually move
out, not all at one time. This gives a smooth even advance.
Let's suppose that the engine has speeded up to its governed speed. At this time, the weights have
moved outward as far as they can. As the weights moved, the hooks on the free end of the
weights rotated the distributor cam in the direction of cam rotation. Now, each of the distributor
cams will strike the rubbing block on the movable point sooner in the cycle, causing the points to
open sooner. This action causes the spark to occur in the combustion chamber earlier during the
compression stroke of the engine, or advance the time the spark occurs.