Well Scott, I had to go back and look up an old Super Ford magazine out of the attic. Miller thought was that the Sharp and Crane rocker arms of the day, as well as the Boss 429 had the pushrod located wrong. Where you drew the line in your video thru the axis of the roller and bearing he agreed with.
That said he referred that the Sharp and Crane rocker arm were designed based off the surface of the roller and valve stem tip. Thus he had Sharp make some rocker arms up using the geometry you show in the video. His Boss rocker had the pushrod cup closer to that axis to minimize the pushrod movement, giving a straighter push on the rocker arm. Jim tried to get Sharp to do all their rocker arms to this geometry. If I am explaining correctly.
OK, I understand. I've talked with Jim several times over the years. I think he would love for people to believe he "invented" mid lift geometry. The only thing he really invented...and patented...was the term "mid lift". Rocker arms have been in use for centuries, and so has "proper" geometry. Geometry is not something anyone invented. It's something we observe. Jim was correct in that the pushrod side of the rocker has it's own geometric requirements like the valve side and I will say, most rockers are not very close on the pushrod side once you get the valve side right. We focus on the valve side for a few reasons; one, we're dealing with the valve. That's what we're trying to control. Two, because of the ratio in the rocker, any errors on that end are going to be amplified more than the pushrod side. Three, we have a guide that will be greatly effected by what we do on that side of the rocker. We can't control both sides of the rocker at once, so we have to pick one. To answer your question, yes, there are rockers that are correct on both sides. The Sharp rockers I have on my 390, once set up to proper mid lift geometry, are very close on the pushrod side. At least for my lift. The pushrod side needs to be the same as the valve side; if you look at the ball on the pushrod (or rocker) as the pivot point of that side of the rocker just as you look at the roller tip as the pivot point for the other side, then you apply the same technique; you find the center of the ball, draw an imaginary line through it and the center of the rocker pivot (shaft in this case) and that line should be 90* to the
pushrod at mid lift. I've worked with Sharp on developing some BB Chev stud mount rockers for AFR that are correct on
both sides at .700" lift. We offer them as sets and AFR also now recommends them to their customers.
One thing to keep in mind; there is NO industry standard for roller tip rockers. The OEM's never used them on any of these American engines we are familiar with, so there is no design standard. That's why there are more versions and "designs" of roller tip rockers than one can shake a stick at. The best rocker IMO used to be the Crane Gold, but they seem have to gone off shore and are no longer the same rocker they once were. We've been using Sharp for all our rocker needs for the last few years and been very satisfied. Too many other companies try to build a rocker that fits more than one application and while, for most deals they will
work, most are not right when you try to set them up correctly. I get a dozen calls on this subject a week.
