IMM Engines 408 build

nm9stheham said
Your narrowest sweep will occur when a line between the rocker's center and the contact point of the roller on the valve tip is 90 degrees (perpendicular) to the axis of the valve with the lift at mid lift. Being off-center with a roller is not of any consequence as long as it is not waaay off near the edge. That is why the advice to center to roller on the tip is plain foolish: when you do that, you can move far away from the optimum geometry.

Think of it this way:

With a certain valve length and lift, then the rocker's center HAS to be at a certain height (to get that 90 degree relationship described above).

Once that is set, then the ball/socket is set at a certain height and that fixes the pushrod length.

Not sure what you mean with the last statement about 'interference to the rocker center'??? If you don't want to move the rocker center then you have to change the valve length. Then you get into the optimum ball and pushrod cup location for geometry on the other side of the rocker; then the pushrods may change. That is an issue with all of these rocker setups: you simply have too few adjustments available to make it optimum without moving centers of rotation or valve or pushrod lengths.

BTW how much lift do you have with that SC cam?

While looking at the valve tip the sweep mark leaves a equal amount on the valve tip on each side of the sweep. When I say equal amount it's where the rocker tip does not roll on the valve tip. Another words if it rolled more toward the exhaust side than the intake side then I would say that the sweep is not centered.

nm9stheham said
Not sure what you mean with the last statement about 'interference to the rocker center'???

If I make any adjustments would it throw off the centered sweep of the rocker on the valve tip. As in if I try to make the sweep narrower ... then it would make the centered sweep off.. like more towards the exhaust side or more toward the intake side.

nm9stheham said
how much lift do you have with that SC cam?

Cam specs: