Just from looking at Ducati heads I noticed most valve tips show a nice triangle above the rocker openings when viewed from the side, and that is what I try to use for the “correct” length after the seats are finished. If too long then the opening shims are quite small, and they are rather long if the valve is too short. If cut correctly then they will often be in the 3.5 to 4.5mm range, rather common sizes.





This one is unfinished.


This one might be a tad short. But I may sink the valve a bit more.


The installed length also matters because it seems that the circle for the half-rings is usually about 11.5mm below the tip. Similar closing shim problems result if cut too low or high. And cutting it too far down might result in conflict with the valve seal (not really sure of that). 11mm works fine.

Perfect, if not much done to the seat.


Might result in a really thick closing shim - like 8+mm


And this might be in the 5+mm range. And that is as low as Ducati provides.


Having said all this, many intake valves are 97 to 98mm long, and exhausts 95mm or so long on the 750 and 900 heads. And 1 or 2mm longer on the small chambers of the 500-650 heads. This is just my experience in my limited time trying this. Modified - you are on your own - and everything is custom.

Hope this helps someone.

dearest mike, you have done an excellent analysis on all the possibilities and performances, the #p# cams on the point of maximum opening of the intake valve the goniometer reads 103, 104 degrees, as a racing cam axis should be, I have not never tried and tested other types of camshafts, I have always used P camshafts because I have always had them available and in Italy they were replicated quite well by hold racing spare parts, by Mario Sassi before it passed away.

you are confirming all the work and findings of hours and hours of work, I also have these references and I adjust myself with these reference points, for example by looking at the valve stem that comes out of the profile of the tappet cover.
I often use the original intake valve to mount it on the exhaust, the length is excellent.
great job mike, very helpful for everyone

Thank you for the complements Carlo. It means a lot from you. I only wish more would post what they experience. MikeV

Dear Mike, I have to publish a job I'm doing, but I never find the time.