so whats the difff from 1.6 and 1.7 rockers?

 

The lift ratio. A rocker arm is a lever, with the short side over the push rod and the long side over the valve tip. If you look at cam specs, you'll see lobe lift, lets say that's 0.500" (that's unheard of for a SBF, but we'll use it anyway)

If the rocker arm ratio was 1.0, that means it's 1:1. Meaning for every .1" of lobe lift, you'll get .1" of valve lift. Stock Windors are usually 1.6, which really means 1:1.6. So for every .1" of lobe lift, you'll get .16" of valve lift.

Using the above example of .500" of lobe lift, a 1.6 ratio rocker arm will give you .800" of valve lift (.500 x 1.6).

If you increase the ratio, you'll get more lift and more duration. That will usually give you a little more power.

If you increase the ratio to 1.7, valve lift is now .850" of valve lift. It's only an increase of .050" of lift, but it does make a differance.

This simple swap also provides about 2-3* more effective duration out of the cam. Wait! Don't say it yet! Some one is about to shout that the only way to increase durition is to change the cam. Keep in mind that effective valve lift is generally accepted to be .050". That's at the point where the gasses start to move, and make an effect on the power band. An increased rocker ratio will get to .050" lift about 1-1.5* sooner, and last 1-1.5* longer. Effectivly increasing duration.

 

Pretty much what he said. But like it is shown in the Bolt on myths thread I posted earlier 1.7's on a stock setup doesn't always help.

.boB, Do you have any pics of your FFR Roadster???? I can't wait to get the money to build one.

 

1.7 on a stock motor is a waste

 

>> .boB, Do you have any pics of your FFR Roadster???? I can't wait to get the money to build one. <<


I'm at work now, so I can't access the site. But visit photobucket, and do a search on "bobcowan". There's a bunch of pictures there, including the dyno sheet.

 

Kick *** .boB, I have been wanting one of those cars since I was a kid. Did you buy the engine as a crate from FFR or put it together yourself? I love those intakes!