Quote: The only math class I ever did good in was geometry so I can follow along with all the geometric theory part very well but still have a couple questions about the real world.
So is the effect of scrub really more important than valve lift/timing effects on the power/reliability of normal street/strip engines with roller rockers? Seems scrub would not be very important with a roller tip as it would be with a sliding type rocker tip, within reason of course.
Maybe say in a lift limited class where your valve opens to max lift for more than just a degree or two, would you want to set it up so it is perpendicular to the valve at max lift where the ratio is the highest?
Perpendicular to the valve is where the highest velocity will be so setting the valvetrain up to achieve that is a really bad idea. You want the valve to open quickly and slow down as it reaches full lift. This is very important on lift rule classes because it gives the cylinder more time to fill when the head is flowing its best. Slowing down the valve opening to gain a couple thousandths of lift would be counterintuitive when you could just get a cam that would give the right lift with correct geometry.
I think with the roller tip, scrub should be minimized overall which will give the maximum effect of the cam lobe at the valve throughout the lift range. In addition, it will minimize wear and prolong spring life among other advantages.
Mike Beachel
I didn't write the rules of math nor create the laws of physics, I am just bound by them.
