Rocker Question

[cudabob496]

If 1.5 stamped steel rockers have 150,000 miles on them, how much lower
would the 1.5 ratio be, due to wear?

[Chryco Psycho]

nothing , as long as here is no free play , the rockers tips are probably worn though

[dodj]

1.49999899979

[vinb]

I used to check many  340 stock stamped rockers, ratios were 1.41 to may be 1.46  , Your push rod will  put a hole in one before the ratio changes.

[cudabob496]

so the cup the pushrod is in, and the tip, wear at the same
rate, so the ratio does not change??  I'm confused.

[jhaag]

Rocker arm ratio is measured on a horizontal plane. The ratio is the distance from the center or pivot point to the center of the tip that contacts the valve, divided by the distance from the pivot point to the center of the pushrod cup. As an example 1.5 / 1 equals a 1.5 rocker ratio. Wear does not affect the ratio. Only moving the pivot point changes the ratio. (everything else being equal) Any wear that occurs has no affect on ratio. So explain why you think wear changes ratio...

[cudabob496]

Rocker arm ratio is measured on a horizontal plane. The ratio is the distance from the center or pivot point to the center of the tip that contacts the valve, divided by the distance from the pivot point to the center of the pushrod cup. As an example 1.5 / 1 equals a 1.5 rocker ratio. Wear does not affect the ratio. Only moving the pivot point changes the ratio. (everything else being equal) Any wear that occurs has no affect on ratio. So explain why you think wear changes ratio...

I will, but first can you explain this?

"Another important note is that the Rocker Ratio is always changing because the Rocker Arm tip is moving on an arc around it's center pivot point, but the valve stem goes straight up and down. This means that as the Rocker Arm moves, the distance from the pivot point to the contact point on the valve stem is always changing.  If this distance is changing, the Rocker Ratio is also changing.  Typically, the amount of change for a nominal 1.5 Rocker Ratio in a pushrod engine is from 1.45 to 1.55 as it goes through it's arc. For Over Head Cam valve trains, the change in Rocker Ratio is much more dramatic.  It is not unusual for the ratios to change from 3.0 to 1.5 during the entire valve lift event."

[Chryco Psycho]

as the hydraulic lifter adjusts for play the ratio has to stay the same so if one end moves X the other end has to move Y

[Strawdawg]

The rocker moves in an arc rather than straight up and down.  Thus when you measure from a horizontal plane as mentioned above, the tip of the rocker has a slightly different length from the rotation axis when a line is projected down from the horizontal plane.  At maximum "throw", the effective length is minutely less so the rate of valve movement with rocker displacement is not linear. 

It has nothing to do with wear.  It's simply geometry at work.

[cudabob496]

I guess I must have been thinking about "effective" rocker ratio then. Obviously per the strict definition,
it does not change, if its just a ratio of lengths.  I think my mindset was, if you increase rocker ratio, you increase
valve lift. If you decrease rocker ratio, you decrease valve lift.  So, if figured, if the tip of the rocker arm wears, due to
age, that will decrease valve lift, which also occurs if you decrease rocker ratio. But, the two are really not related, I suppose.