Originally Posted by ChevroletSS
Ok can you explain rocker arms to me? What is 1.5, 1.6, 1.7 rockers and what are the differences. Are there others??? I am ging to post another thread on this to so others can comment
The rocker arm is a fulcrum. Its job is to turn the cam lobe's circular rotation into an up and down movement. This is able to be done because the rocker has a pivot point or fulcrum that allows the cam lobe to open the valve.
The rocker arm's pivot point is not in the center of the rocker; instead it is offset more towards the pushrod. The amount of offset is expressed as a ratio (1.5, 1.6, 1.7, etc.)
The stock small-block Chevy rocker arm has a 1.5:1 ratio. These rockers are called 1.5 ratio rockers or just 1.5 rockers for short. This means that the rocker arm tip at the valve end of the rocker moves 1.5 times the amount of movement seen at the pushrod end of the rocker- which is also the same amount as the camshaft's lobe lift.
Let's say your camshaft has 0.350" lobe lift. With a 1.5 rocker, the cam's lobe lift becomes 0.525" lift at the valve (0.350 x 1.5 = 0.525).
The same 0.350" cam lobe using 1.6 rockers would give you 0.560" lift (0.350 x 1.6 = 0.560), w/o having to remove and replace the cam. With the Chevy factory hydraulic roller cam and lifter set up, this will give you more lift before running into problems w/the dogbone retainers losing contact w/the stock lifters.
Changing the rocker ratio will also change the off-the-seat duration seen at the valve a small amount. However, seat-to-seat duration will not change.