How much lift and duration on a hyd. Roller??

[fe66comet]

How much lift and duration is possible on a hydraulic roller before the lifter scrubs the cam lobe? Of course duration would change how much lift and overlap. Any ideas?

[blykins]

Scrubs the cam lobe?  What do you mean?

I have ran about .660" lift with an FE hydraulic roller before.  Frequently use low to mid 250's on .050" duration with larger engines.  I don't know what you mean by scrub the cam lobe though. 

[CaptCobrajet]

I have never seen that be an issue.  Even a "full body" roller should not come close to contacting the lobe.  Hydraulic rollers have large base circles and slower opening ramps than solid rollers.

[fe66comet]

The hydraulic rollers I have certainly do not have the clearance that a mechanical lifter has. The body extends way past the centerline of the wheel. The advantage of a roller is steeper ramps to hold the valve open longer so the roller prevents the edge of the lifter from contacting the cam as in a flat tappet. What I am seeing in the market is basically a .600-650 lift max with almost .300 duration, with the FE maxing out around .610 or so. One thing for sure the body on the hydraulic lifter has a lot more front and rear overhang than the mechanical lifters do.