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Yes. (Snip)...
Edit 5-31-2009 by Tim Engel
No. As it turns out, there's no difference between the J-H and Lotus versions of the cams and pulleys.
ONLY on the 110°/100° "DUAL"-MOP pulley, the 100° MOP blue-dot is really 97° MOP. The pulley's geometry/ math simply does not support 110° and 100° co-existing on the same pulley. So Lotus cheated the 100° timing dot over to the nearest whole tooth, and that was 97°
100° = 100° on a Single-MOP, blue-dot pulley.
100° = 97° on a "Dual"-MOP 'cheater' pulley.
If you're just timing factory-stock pulleys with blue-dot/ 100° MOP timing marks, then just align the dots and don't worry about the details.
If you're trying to check the cam timing with a degree wheel, the Dual-MOP 100° blue-dot will throw your math a curve... it's really 97°.
Apparently, for the 110°/100° "Dual" MOP pulley, Lotus thought it would be less confusing to just stick with the same old blue timing dot (blue = 100°) rather than have to explain what 97° was doing in the mix. However, in the long run, their little 'cheat' seems to have caused more confusion that it has saved.
There are minor dimensional differences between early and later pulleys (rim centering on the hub, etc), but they are inconsequential to fit, and they don't alter timing.
Interchange to your heart's content.
Lotus timing dot colors:
110° MOP = Red Dot
104° MOP = Green Dot
102.5° MOP = Yellow Dot
100° MOP = Blue Dot
115° MOP was JH-only. Lotus never used it, so they didn't assign a timing dot color to it. But whenever I have seen a paint color with 115° it has been white.
Regards,
Tim Engel
Last edited on 06-17-2019 12:57 am by Esprit2