Re: Rocker Arms
 

I reserve the right to be wrong, but I believe the Nascar teams have experimented with larger ratio rocker arms in order to reduce the amount of spring pressure on a given lift/duration. Less spring pressure should equate to less parasitic hp loss within the valve train.

Re: Rocker Arms
 

On another thread, I remarked about a 283 racer who went through about 100 stamped OEM rockers to get the 16 that he used. That was back in the day when OEM was all that was allowable, and the best arms were the ones with the little triangle on top of the tip above the valve stem tip.I don't know ,however, if he was attempting to achieve accurate lift, or whether he was striving for as accurate a ratio as possible.With all the latitude that various length pushrods can produce,there is an almost infinite degree of possibilities. Yes, it's interesting what an open forum can produce.Thanks to Travis for the expose' on how rocker arm ratios are calculated.

Re: Rocker Arms
 

The higher ratio rocker arm will increase any action ground into the camshaft profile by a mathematical amount. One of the limitations of how radical a camshaft profile can be ground is the lifter diameter. So, when the camshaft has been designed to maximum acceptible rate of lift change dictated by the lifter diameter, then there is no more that can be done to make the valve open any more at a given lobe lift. The higher rocker arm ratio allows a little bit more lift at a given lobe lift, hence "more area under the curve". Also, you can grind a faster ramp into a camshaft profile if the lobe lift is less, also providing for more area under the curve.

See what Alan said above. If I could draw pictures here, it would be easier to see.

Re: Rocker Arms
 

Ain't that the cryin' truth.

Re: Rocker Arms
 

Elgin part number for the 7/16 rocker arms is R-1840.The rocker arm ball isn't included and the part number for the rocker arm ball is RM-1000. Don't try and use a big block ball. It won't fit down in the arm. 7/16" screw in studs and poly locks are everyplace . I've had to do other things on other engines to make stuff right such as using different length push rods on some valves. Good luck on your project.I'm in the middle of this on a 327 I'm doing for my Chevelle. Short block's done, I'm assembling and sorting out the heads and the valve train,now its time to measure lobe lift and compare it to total lift. One more thing to do.

Re: Rocker Arms
 

Well at least the lowly AMC came with 1.6 rockers and .903" lifters...:p

Re: Rocker Arms
 

Some of the latest Spintron "best results" have been with reduced ratio rockers and cam lobes that are larger diameter and shaped quite a bit different than what was once thought good. Less deflection, less spring pressure, less failure, sometimes more power!