original Ducati cams timing figures

[Eldert]

Hi Guys

i checked some Original Ducati cams this week . keep in mind that these are about 40 to 50 year old parts measured with used rockerarms
i took the readings at 1 mm with no running clearence . lift is camshaft lift

Gray cam intake opens 35 close 49 duration 264 degrees lobecentre 97 degrees . lift 9.2 mm
----------- exhaust opens 52 close 32 duration 264 degrees lobecentre 100 degrees . lift 8.6 mm

Red cam intake opens 45 close 53 duration 278 degrees lobecentre 94 degrees . lift 8.6 mm
---------exhaust opens 60 close 41 duration 281 degrees lobecentre 99.5 degrees . lift 8.25 mm

White cam intake open 16 close 50 duration 246 degrees . lobecentre 107 degrees . lift 8.5 mm
-----------exhaust open 45 close 13 duration 238 degrees . lobecentre 106 degrees . lift 8.15 mm

i posted the green / white camshaft specs some 3 years ago but i repost them anyway

green /white cam intake opens 41 close 64 . duration 285 degrees . lobecentre 101.5 degrees . lift 9.9 mm
-------------------- -exhaust opens 66 close 29 . duration 275 degrees . lobecentre 108.5 degrees .lift 8.55 mm

Eldert

[DewCatTea-Bob]

[quote= Eldert ...
" i checked some Original Ducati cams this week . "

____ Thanks for letting us know the 1mm valve-lift figures for these cam-models, Eldert !
(Even-though they are worthless for direct-comparison with the FACTORY-figures, these 1mm.type timing-figures can possibly better help others to determine their installed camshaft-model.)



" lift is camshaft lift "

____ I assume that you mean that your lift-figures are actually the height of the cam-lobe, rather than the actual 'valve-lift' ?



" Gray cam
intake lift 9.2 mm
exhaust lift 8.6 mm "

____ The 'Gray-cam' is the 'Mach-I camshaft-model', and every-one I've ever measured had lobe-lifts of pretty-much exactly 9mm-(intake) & 8.5mm-(exhaust) ! _ (Although the 1.04 to 1 rocker-ratio would make the actual valve-lift 4% higher.)



" Red cam
intake lift 8.6 mm
exhaust lift 8.25 mm "

____ The 'Red-cam' is the n-c Mark-III camshaft-model, and every-one I've ever measured was pretty-much exactly 8.5mm-(intake) & 8mm-(exhaust).
__ As a side-note,, there's also an obviously different w-c 'Mark3' camshaft-model, with spec.figures which are neither the same as the red/Mark-III nor the gray/Mach-I camshaft-models,, yet it's been color-coded as 'gray' (according to w-c.parts-books).



" White cam
intake lift 8.5 mm
exhaust lift 8.15 mm "

____ WHICH 'white cam' ? _ As there are at-least four different Scrambler-model camshafts which were all color-coded as 'white' ! ...
First there was the n-c/Motocross camshaft-model, which has lobe-lifts of about 7.8mm-(intake) & 7.6mm-(exhaust).
Then next, there was the 1967 w-c 250-Scrambler camshaft-model, (which I currently don't have the specs for).
Then there was the 1968 w-c Scrambler camshaft-model (and also another w-c.250SCR cam.model), which have about 8 or 8.2mm-(intake) & 8 or 7.8mm-(exhaust) lobe-lifts.
__ I-myself have never found any white/Scr.cam with a lobe-lift as high as "8.5 mm" !
If that measurement is actually not a 'typo', (as I doubt that Eldert possibly made a 'measuring' error), then I suspect that HIS white-cam example was originally taken from a (non-USA)- 450-Scrambler which had a REAL/actual 450-Scrambler camshaft-model factory-installed (rather than the 1968 w-c.250-Scrambler camshaft-model which seems to be the ONLY camshaft-model factory-installed in ALL non-DESMO 450-models made for the USA).
If so, then Eldert is pretty-lucky to possess THAT-cam, as that model is one of the very-few cam.models which I don't have within my near complete OHC.shaft-collection,, and it ought-to perform quite-well within a 350-engine !



" green /white cam
intake lift 9.9 mm
exhaust lift 8.55 mm "

____ There are TWO different green&white camshaft-models ! ...
The '250F1-cam', which I believe has lobe-lifts of about 9.85mm-(intake) & 8.35mm-(exhaust),, and
the '350M3-cam', which I believe has lobe-lifts of exactly 10mm-(in.) & 8.5mm-(ex.).
The two G&W.cam-versions can be most differed by their quite different 'overlap' valve-timing, as the F1.cam is MUCH wilder (and pretty-much un-extra beneficial for other than a [higher revving !] 250-engine).


Dukaddy-DUKEs,
DCT-Bob

[LaceyDucati]

Thanks Eldert, for sharing your findings.

I will add some figures I have taken some time ago at 1mm lift using zero clearance.

Grey - intake opens 34.5 closes 49, Actual lift at the valve 8.5mm, Lift measured from the cam 9.05mm
exhaust opens 51 closes 28, Actual lift at the valve 7.9mm, Lift measured from the cam 8.46mm

Green and white - intake opens 34.5 closes 61.5, Actual lift at the valve 9.67mm, Lift measured from the cam 9.90mm
exhaust opens 60 closes 33.5, Actual lift at the valve 8.05mm, Lift measured from the cam 8.55mm

Actual cam lift is always less than that what can be measured on the cam, so if there is a "ratio" to the rocker it is the other way to what you suggest Bob. I too have measured lots of cams and besides small variation in base circles the cams seem fairly consistent when measured with a vernier. The lift measurements I have taken for these two types of cams are consistant when measured with a vernier. Cam timings however I have found to vary a bit, this I am sure is down to cam grinding, variations in rocker geometry and variations in rocker pin hole positioning. Yes believe me they are not as accurate as you would think! I have proved this by swapping rockers around and trying the same cam in different heads, no wonder they quoted +/- 5 degrees! However In the real world +/- 5 degrees is not going to make a lot of difference in my experience.

Being involved in the manufacture of parts for these engines, I have to measure the original components in depth and I begin to notice things I wish I hadn't! The other day I was getting the crank to gearbox shaft pitch measured on a CMM measuring machine to check the pitch was 93.0mm as I was expecting. We measured 9 cases which varied from 92.847mm to 93.11mm, that's a variation of 0.263mm, welcome to my world! Always wondered about those +/- gears Ducati made for the crank, I don't think it was for wear as many think! Ignorence is bliss and a desireable state to be in when enjoying owning 60's motorcycles

Sleep well

Nigel

[DewCatTea-Bob]

[quote= LaceyDucati ...
" I will add some figures I have taken some time ago at 1mm lift using zero clearance. "

____ We're certainly glad to have you chim-in as well, Nigel !



" Grey -
intake Lift measured from the cam 9.05mm
exhaust Lift measured from the cam 8.46mm

Green and white -
intake Lift measured from the cam 9.90mm
exhaust Lift measured from the cam 8.55mm "

____ It's assumed that those "Lift" figures are the actual max.height of the 'cam-lobes' themselves.
__ Your lift-figures for the gray/Mach-I camshaft-model are certainly those of (ONLY just) the n-c.250Mark-3 & Mach-I Duke-models,
cuz the w-c.Mark-3 camshaft-model (which is also considered to be a 'gray-cam'), has quite notably reduced cam-lobe lifts -(of 8.5 & 7.8mm) !
__ Concerning your Green&White-camshaft example,, telling only by just the given "Lift" for the exhaust-lobe, I'd say that it's most-likely a '350Mark-3' camshaft-model (and not a 250F1-model version of a G&W.cam).



" Actual cam lift is always less than that what can be measured on the cam, so if there is a "ratio" to the rocker it is the other way to what you suggest Bob. "

____ That's fairly disappointing to learn-of -(as I've never actually double-checked for myself),, but your revelation is a relatively important finding, so thanks very-much for your posting-info Nigel !
(Of-course I wish I could go-back & take-back that evidently incorrect info I've previously posted,, however instead, I did add some other-stuff which I had failed to include in that post before, [thus the now included 'DCT-Bob'].)
__ I was quite confident of my previous-post's related stated-claim (concerning the resulting effect of the rocker-ratio), because that info was given to me by a highly-informed RESPECTABLE-source -(John White of DomiRacer), who was my main & top-notch Ducati-mentor (of the early-70s) ! _ So I've always trusted & remembered it ever-since he told me that Ducati's "rocker-ratio" was "1.04:1" ! _ And I had even followed-up & asked if that ratio helped or hindered the ACTUAL valve-lift, and I'm almost as certain that he had confirmed that the ratio-effect was positive (rather than negative as you've now presented).
__ Your-own findings indicate rocker-ratios* of:
'.94 / 1.065' -(intake) & '.934 / 1.07' -(exhaust), with your "grey cam",, and
'.977 / 1.024' -(intake) & '.94 / 1.06' -(exhaust) with your "green and white cam".
So YOUR rocker-ratios are-not so very consistent, (probably for the various reasons you've mentioned in your post), but average-out at about '.948 / 1.055 : 1' .
(* The two figures listed per rocker-arm are the results of whether negative or positive lift-effect.)



" I too have measured lots of cams and besides small variation in base circles the cams seem fairly consistent when measured with a vernier. The lift measurements I have taken for these two types of cams are consistant when measured with a vernier. "

____ I very-much agree, as that's* also been my-own experience with those and ALL other like-kind camshaft-models !
(* That while the base-circle of a particular cam.model may vary somewhat, the actual 'lobe-lift' figure remains MUCH-more consistent !)
__ However, I should like to point-out that the base-circles of n-c & w-c camshaft-models are quite OBVIOUSLY different, as the w-c.camshaft-models have a rather significantly smaller base-circle !



" Cam timings however I have found to vary a bit, this I am sure is down to cam grinding, variations in rocker geometry
no wonder they quoted +/- 5 degrees! "

____ Indeed so, at-least Ducati managed to get their camshaft valve-timing established somewhere within just a 10-degree window !


Dukaddy-DUKEs,
-Bob