[Stan Weiss]

Originally Posted by Steve C.

"The solids loose about 10 degrees of duration right off the bat from lash so there's that."

Related, here was a question and the answer from Mike Jones / cam designer:

Mike, you may have already tried to explain it, but why the added duration for a solid lifter cam vs the same spec. hydraulic-cam??


If you want the valve lift curve to be the same, the solid(Mechanical) lifter cam will be bigger at .050".
That's because with the hydraulic lifter you start opening the valve at around .004"-.006" lifter rise, so .050" lifter rise is .044"-.046" above the point the valve is opening. Now, with the mechanical lifter you start opening the valve at the hot lash point divided by the rocker ratio(normally around .012"-.016" lifter rise), so .050" lifter rise is only .034"-.038" above the point the valve is opening. So if you only look at the lift above the point the valve is opening, you're trying to compare the duration @ .045" on the hydraulic cam, with the duration at .036" on the mechanical cam.


.

Steve,
Cam companies have known about and been playing game with this for a very long time. In the late '60s I had an Engle solid cam for a SBC that had 0.012" Intake valve lash.

0.012" / 1.5 = 0.008" almost the same as a hydraulic cam.

There are still tight lash solid cams available today.

Stan

PS - Let me also add that using tight lash ramps is one to make a solid cheater cam that will improve performance while still having the same lobe lift and 0.050" duration as the original cam.

Also some place (like SCCA) don't let you vary anything or it is illegal