What ratio VW rockers are best?
We recommend 1.4 rockers (which DO work on stock engines). 1.25 rockers give you almost no gain for your work; waste of effort.
How is rocker ratio calculated?
The ratio of a rocker arm is determined by the distance between the centerline of the pivot point to the centerline of the roller tip (or area of contact with the valve stem), divided by the centerline of the pushrod to the centerline of the pivot point (X).
What do high ratio rockers do?
A high-ratio rocker arm increases valve lift at every point. It boosts gross valve lift by several hundredths of an inch, but it can make a camshaft seem a few degrees larger as well.
How to calculate the change in rocker ratio?
The proper way to determine how much change ratio rocker yields is to divide the lift of the cam by the original rocker ratio (this number is referred to as the lobe lift of the valvetrain), then multiply the lobe lift by the new rockers ratio. For example, an F-303 Ford Racing small-block cam has a 0.512-inch lift at the valve.
How does the ratio of rocker arms affect valve lift?
In order to find how a ratio change in the rocker will affect the lift, you must divide this number by the stock ratio of 1.6 to get the lobe lift of .320 of an inch. Multiplying this .320-inch lobe lift by the new rocker ratio 1.7 results in a new lift of .544 of an inch in valve lift.
What can you do with split ratio rockers?
In retrospect, you may want to increase the duration of your intake slightly, and again this type of modification will result in improved flow numbers. Utilizing split ratio rockers can also be used as an effective tuning tool to dial in a combination, but yet again, the same effect can be achieved with a custom camshaft.
Is the intake and exhaust of a camshaft the same?
If you’ve ever looked at a cam card (furnished with each new camshaft), you’ve probably noticed that some cams have the same specs for both the intake and exhaust (single pattern), while others differ (dual pattern).
The proper way to determine how much change ratio rocker yields is to divide the lift of the cam by the original rocker ratio (this number is referred to as the lobe lift of the valvetrain), then multiply the lobe lift by the new rockers ratio. For example, an F-303 Ford Racing small-block cam has a 0.512-inch lift at the valve.
In order to find how a ratio change in the rocker will affect the lift, you must divide this number by the stock ratio of 1.6 to get the lobe lift of .320 of an inch. Multiplying this .320-inch lobe lift by the new rocker ratio 1.7 results in a new lift of .544 of an inch in valve lift.
In retrospect, you may want to increase the duration of your intake slightly, and again this type of modification will result in improved flow numbers. Utilizing split ratio rockers can also be used as an effective tuning tool to dial in a combination, but yet again, the same effect can be achieved with a custom camshaft.