roller rockers
02-20-2007, 09:36 AM
#2
4th Gear Member
Join Date: Jul 2006
Location: The Great State Of Texas
Posts: 1,062
RE: roller rockers
See if this helps
The Math
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). Most aftermarket roller rockers have the ratio stamped on them.
To determine the change in lift when changing rocker arm ratios, divide the lift of the cam by the original rocker ratio (which gives you the lobe lift), then multiply this number by the new rocker ratio. For example, the stock Mustang 5.0L HO cam has .444” at the valve. Divide this number by the stock rocker ratio of 1.6 to get the lobe lift, .2775” and multiply by the new rocker ratio 1.72, to get the new lift of .477”.
[IMG]local://upfiles/41956/3A239AB7408C4772AA129E3C3912D919.jpg[/IMG]
The Math
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). Most aftermarket roller rockers have the ratio stamped on them.
To determine the change in lift when changing rocker arm ratios, divide the lift of the cam by the original rocker ratio (which gives you the lobe lift), then multiply this number by the new rocker ratio. For example, the stock Mustang 5.0L HO cam has .444” at the valve. Divide this number by the stock rocker ratio of 1.6 to get the lobe lift, .2775” and multiply by the new rocker ratio 1.72, to get the new lift of .477”.
[IMG]local://upfiles/41956/3A239AB7408C4772AA129E3C3912D919.jpg[/IMG]
02-20-2007, 02:41 PM
#6
6th Gear Member
Join Date: Nov 2005
Location: Rochester, NY
Posts: 8,467
RE: roller rockers
This part:
is an accurate explanation. In short, 1.7 rocker arms basically open the valves farther than 1.6 rockers. The part i just quoted explains how to find the new lift with a 1.7 rocker. Most cams have their lift rated with use with 1.6 rockers, which is why you need to do that math to find the new lift with 1.7s...
To determine the change in lift when changing rocker arm ratios, divide the lift of the cam by the original rocker ratio (which gives you the lobe lift), then multiply this number by the new rocker ratio. For example, the stock Mustang 5.0L HO cam has .444” at the valve. Divide this number by the stock rocker ratio of 1.6 to get the lobe lift, .2775” and multiply by the new rocker ratio 1.72, to get the new lift of .477”.
02-20-2007, 03:51 PM
#8
4th Gear Member
Join Date: Jul 2006
Location: The Great State Of Texas
Posts: 1,062
RE: roller rockers
ORIGINAL: pastfast125
how much lift can you safely run with everything stock and not have clearance issues or valve spring bind?
how much lift can you safely run with everything stock and not have clearance issues or valve spring bind?
