Hey Plainview,
I'm not trying to be a butt-head with my questions, but really just curious about what published specs on a supplier's cam means to the average buyer. And, then what cam timing does to the valve opening and closing events.
How did you determine the cam timing of the LCE cams with ground in advanced? Where in their specs do they publish CAM TIMING? Where in their published specs do you see OVERLAP DEGREES?
If you see the Lobe Separation Angle in the cam spec, will that tell you the Intake Centerline?
Geezzz…I’ve played with cam timing in the EA software a zillion times!
Gnarls.
Forgive me, I assumed you knew the term "cam timing." It's simply the lobe positions, the ICL and ECL since those numbers are referencing degrees of crank rotation or in other words how the cam is timed in relation to the crank. Most manufacturers publish the lobe positions and many, like LCE, also publish the valve opening and closing events which could be calculated from duration and lobe centerlines anyway.
As for determining whether a cam has advance ground into it - When the ICL and ECL are the same (and they will equal the LSA when this happens), the cam is said to be ground "straight up" with no advance "ground in" to the design. It appears this is the way Comp Cams grinds their cams for the 22R/E. All the ones in their catalog have ICL=110, ECL=110 and the resulting LSA=110. Again, remember that LSA is simply (ICL+ECL)/2.
Now, let's say you have a cam where the ICL=106, the ECL=114 and thus the resultant LSA is still 110. That cam would be said to have 4 degrees of advance "ground in" to it. The lobes are in the same positions they'd be if it was ground straight up and you used an adjustable cam gear to advance it.
LCE has a grind with 8 degrees advance ground into it. That's the most I've seen from any cam manufacturer for the engines I'm familiar with. Most of their cams have less.
I don't pretend to know why that much advance is necessary, I can only assume they tested that cam and found that for the type of engine they expect/recommend it to be installed in it worked best.
Generally speaking, advancing a cam increases cylinder pressures at lower RPMs and thus tends to move the torque curve down in the RPM range. Retarding does the opposite.
As to what these numbers mean to the "average" purchaser - I'd guess not much. I think most people just choose a cam based on the recommendations of the supplier and maybe their friends/other hobbyists and they don't really worry about the numbers.
Those numbers are there for people like you and me who want to know more than the average person and have a solid base of knowledge on which to make meaningful comparisons.
