Valvetrain Geometry
Thanks to @gzig5 for sending me an old style PRW 1.6 rocker to compare to the new style. The data in the first picture shows the results of actual valve motion testing of the two rockers. The rest of the pictures show the differences in the two. Old rocker is shiny, new one is dull. In the picture with both rockers on the shaft, the old style rocker is in the background.
There is no real difference in the valve side of the rocker arms except for the shape of the long arm. Looks like it was changed to increase spring clearance. The fulcrum length (distance between the rocker shaft centerline and the roller tip centerline) does measure a bit different between the two, but that could just be manufacturing tolerances. These are Chinese rockers and even the new rockers vary by several thousandths from rocker to rocker.
The real change in the rockers is on the pushrod side. The angle of the adjuster and the adjuster arm has been changed. The old rocker could be considered a '90 degrees in valve closed position' rocker. The new rocker could be considered a '90 degrees at mid-lift position' rocker. In this regard the new style rocker is an improvement over the old.
If you look closely at the second picture you can see a couple of other differences. The old style rocker has two individual bushings with a space between. New style is one solid bushing with a small machined groove in the center for oil distribution. Look closer and you can see the valve side oiling holes. The old style has a larger hole that feeds oil onto the top of the rocker. This hole is not restricted in any way and with 8 rockers on each shaft it's hard to see how there could be any shaft oil pressure. The new style oil hole is smaller, under the long arm and is drilled off-center. The off-center location restricts the oil flow and would help to maintain oil pressure in the shaft. Seems like shaft oil pressure would be important in a bushing style rocker.
One thing I do like about the old style rocker - the roller tip protrudes farther than the two arms.
Thanks to @gzig5 for sending me an old style PRW 1.6 rocker to compare to the new style. The data in the first picture shows the results of actual valve motion testing of the two rockers. The rest of the pictures show the differences in the two. Old rocker is shiny, new one is dull. In the picture with both rockers on the shaft, the old style rocker is in the background.
There is no real difference in the valve side of the rocker arms except for the shape of the long arm. Looks like it was changed to increase spring clearance. The fulcrum length (distance between the rocker shaft centerline and the roller tip centerline) does measure a bit different between the two, but that could just be manufacturing tolerances. These are Chinese rockers and even the new rockers vary by several thousandths from rocker to rocker.
The real change in the rockers is on the pushrod side. The angle of the adjuster and the adjuster arm has been changed. The old rocker could be considered a '90 degrees in valve closed position' rocker. The new rocker could be considered a '90 degrees at mid-lift position' rocker. In this regard the new style rocker is an improvement over the old.
If you look closely at the second picture you can see a couple of other differences. The old style rocker has two individual bushings with a space between. New style is one solid bushing with a small machined groove in the center for oil distribution. Look closer and you can see the valve side oiling holes. The old style has a larger hole that feeds oil onto the top of the rocker. This hole is not restricted in any way and with 8 rockers on each shaft it's hard to see how there could be any shaft oil pressure. The new style oil hole is smaller, under the long arm and is drilled off-center. The off-center location restricts the oil flow and would help to maintain oil pressure in the shaft. Seems like shaft oil pressure would be important in a bushing style rocker.
One thing I do like about the old style rocker - the roller tip protrudes farther than the two arms.