This year they switched to roller cams for the big tracks and still flat tappet on the street courses. I was told when they made the change they had all kinds of trouble getting the valvetrain stabilized because the acceleration rate of the roller lifter is so much greater.

You guys want to wrap your heads around something? Check out in-rad (inverse radius) cams, the lobe actually looks like a penut. Made AMAZING power, but at the sacrifice of valve train life.

There are three different pneumatic/electro magnetic systems in development and testing. That will be the ticket for making an engine live with obscene ramp speeds and lift numbers. If they can make the systems last that is. Unfortunately, the millions that had been invested into these systems in years past had all been geared to high rpm longevity and not a life span with regard to hours or years of service.

There are a lot more out there in use than people would think. Including some that have them in their engine without even knowing. Many hot street cars even. If I'm not mistaken, even some HR's.

I know they have some inverse radius solid rollers , they make them in hydraulic now ?

I believe so. So that's not 100%. I could swear I remember someone saying Jones (and some others) does some that way. Again, don't quote ,me.

Oh, you can quote me that some diesels use IR. Obviously, those don't rev high.

No, only SR, and that technology is 20 years old. We were working with Crower in the development of those cams back when Menard was still running V6 Buicks at Indy.

But it seems like some people read a tech article about "new technology" and the real pros are the ones that have been helping develop and test it for the past 5 years.

yep...merc 377 scorpion motors run a can like this..easy on the valves,,sets them down nice and easy..

Did a quick search, and Here's an old thread with Harold Brookshire and Mike Jones responding to someone asking about IR cams.
Jones does mention use in HR's

http://speedtalk.com/forum/viewtopic.php?t=8711