Is anyone able to expand on the published timing specifications for 907/910 engines? For example, the 104 is described as 272 degrees duration as I recall but from which exact points? Seated, and at specified lash settings? What is known on the duration figures at such lift points as 0.020 or 0.050 inch?

Cheers

Most cams I have seen are measured in degrees @ .50 lift

Not sure how Lotus does it though.  Find and Lotus engine builder who knows is my best advice.

 

atb,

 

Richard

I've found this .xls on here somewhere, with a lot of useful info about the different cams and timing.

Cam_Data.xls

Thanks, Filip, that's a great document. I'm inclined to think the "B", "C", type designations followed on from what was developed for the original Twincam engines native to the early cars. Well respected Dave Bean Engineering of California published a catalog showing figures seat-seat as well as at 0.050 lift, for which the D was 232 versus 220 for the C. Attending a local Club banquet here in 1986 the late Tony Rudd explained and sketched out how the D's lift rate was more aggressive, resulting in considerably more area under the graphed lift curve as opposed to the C. Seems plausible that Lotus, thinking the D to be their best development to date, fitted the early 907 with this only to find it too peaky. 

Cheers