Discussion and questions related to the course How to Degree a Cam
I'm building 2.5i m20 engine for BMW E30. Right now I'm in the camshaft degreeing phase and need some help. I have completed the 'How to Degree a Cam' course and now trying to practice what I have learned.
The camshaft I'm trying to set is Schrick 272/272 (05601720-00).
Unfortunately, the product manual does not specify how Schrick measures cam duration, at what lift do they begin and end the cam duration measurement?
All the data I have is:
1. Cam lift (Valve lift) I/E mm: 7.0 (11.0)
2. Duration *CRA Intake/Exhaust, Peak Timing: 272/272/111
3. Valve Timing *CRA IO-IC-EO-EC: 25-67 67-25
4. Valve lift at TDC I/E mm: 1.6
5. Valve clearance I/E mm: 0,25/0,25
The Schrick catalog says that the duration and timing numbers "are shown minus the ramps". I'm not quite sure what that phrase means. I found true TDC and tried to measure the inlet valve opening and closing events started from zero point and I got IO: 17* BTDC and IC: 56* ABDC. As I understand, the fact that the mismatches are different indicates that the measuring starting point is incorrect.
My question is, does anybody know what could be the Schrick duration @ the IO and IC is measured. Or is there any other method I can use to degree this cam based this information?
I also found a forum post that says: "BMW and Schrick measure 4 cyl cams from ZERO with a special lash setting that is different than the normal cold lash clearances. The cam checking valve lash setting they both use is 0.28 mm between the cam base circle and rocker pad. BMW also shows a different (shorter) duration that can be found with 0.5 mm instead of the 0.28 setting. Six cyl cams use a different setting."
Other post says that technically the Schrick numbers are measured at 0.008" or 0.010" lift depending on the cam, and the BMW factory cams are measured at 0.014" lift.
This weekend I made some tests and got very close results when I set the measurement point to 0.2 mm. The closing point was exact match, but opening point was 1 degree advanced. I also took some measurements where valve lash was set to zero, but the results got worse. It seems to me that the valve clearance should be set exactly at 0.25mm and re-measured at 0.2mm. I didn't have time to try the 0.28mm gap between the cam base circle and rocker pad but I will definitely try it too.
It looks like your measurements match with 0.2mm lift and 0.25mm lash however I'd personally email schrick and see if they can clarify what their valve opening measurement actually relates to.
The Schrick replied to me that since this is an older profile they do not have the standard data sheet, but to set up at a cold engine you will need 1,6mm – 0,25mm = 1,35mm Valve lift at TDC.