Cam timing

[Dave450]

Hi guys - I'm new to the forum. I have some questions for the technical experts.

I have a race Desmo cam in my 450 that I bought many years ago from John Witt-Mann, a name people in the UK will remember from many years back. He told me it was a copy of an Imola cam and gave me the figures in the dim and distant past, but I don't have them anymore. I will not assume that the figures are the same as a genuine Imola cam. I want to find out what the current timing is. What is the accepted method of checking the cam timing for the singles? Is it by using the checking clearance (e.g. 1 mm), by running clearance or by lobe centres? Once I have done this as accurately as I can, I can report back here with the degree figures I obtain, and I will include lift. This may allow some of you to advise further.

I never bothered dialling in the cam while I was racing and I concentrated more on riding the wheels off it to get results, but now, reading some of the posts on this forum, I would be intrigued to find out how well dialled in - or not - this cam really is. The bike is now back on the road as a Sunday scoot.

If the timing is significantly out, is it possible to obtain offset keys for the singles, or is there another way of dialling in the cam? If I can't get offset keys, I will have to make some up - tedious but possible. I would appreciate the advice of those of you who have been there before me.

Dave

[LaceyDucati]

Hi Dave

Factory figures are given at initial lift, which is an airy fairy way of checking things as the rate of rise is very slow. If you give me figures of 1mm lift with zero clearance I can look at the figures for you.

You set a zero clearance by placing a feeler in to take up the the clearance. At this point you may need to loosen up the closers to allow you to turn the engine over (Desmo's don't you just love em!). Mind you if you don't have the original springs installed, you will need to pull up the closing rocker hard and carefully place a feeler gauge to take up the clearance, not the closing clearance as well!. Without the springs you will also need to hold the closing rocker up when taking reading too.

At zero and 1mm lift you would be looking for figures of around inlet opens 52 degrees BTDC closes 76 degrees ABDC and exhaust 78 degrees BBDC closes 40 degrees ATDC. With lift around 12.3mm inlet and 11mm exhaust. That's a sort of average of figures I've taken from Imola Profile cams in Singles. You can work out the lobe centres if you want, but these figures work very well. This all assuming the cam is as described!

Nigel

[DewCatTea-Bob]

[quote= Dave450 ...
" I have a race Desmo cam in my 450 that I bought many years ago from John Witt-Mann,
He told me it was a copy of an Imola cam "

____ Did he mention who the manufacturer of that D.cam was ?
__ Back throughout the '70s, I was in contact with sources who should've known, and I then never heard any tale of an "Imola" camshaft for any SINGLE-model.
I have heard 'tale' of Factory-made Red&White-D.cams made for racing 450D.engines,, BUT-however, it was made clear to me (back at the time, well-before the '80s) that the R&W-D.cam was intended specifically for the 350D.engine ! _ While the 'Gray & White' D.cam was the equivalent 'Special' DESMO-cam specifically intended for the 450-engine.
Does your odd D.cam have any similar paint-code (shown on it's threaded tip-end) ?
Can you provide all the min & max lobe-figures of your particular D.cam ?



" I want to find out what the current timing is. What is the accepted method of checking the cam timing for the singles? "

____ Well, it seems that there's more than one 'accepted-method', but I-myself only find Ducati's method as acceptable ! _ As their figures represent the very-exact points WHEN the valve can possibly cause ANY-change (by either bleeding pressure or beginning to allow pressure to build-up). _ And-thus the degree-readings ought-to be taken just as the clearance-ramp hands-over to the actual lift-ramp of the cam-lobe.
That change-over point ought-to be found by the time the valve has been 'lifted' (off seat) by the same amount as is the factory-recommended running-clearance. _ (So if the normal running-clearance is .004",, thus-then with the v.clearance set at .008", you'd take note-of your degree-reading at the rotation-point when the valve-cap/shim becomes pressured too-tightly to still be rotatable [by finger, as when it's not under any rocker-pressure].)
THIS checking-method is that which is most-likely going-to produce timing-figures which are most-like those specified by the-factory.



" Is it by using the checking clearance (e.g. 1 mm), by running clearance "

____ I believe the 1mm-standard was first adopted by Jap.manufacturers, and there's of-course nothing magical about that point or even with any slight particular-logic that the resulted timing-figures could possibly represent, as absolutely NOTHING of any noteworthy change happens to always-occur at THAT particular amount of valve-lift ! _ So therefore, (other-than for mere comparison purposes), the 1mm-standard is without particularly-noteworthy logical-reason for existing, and-thus 'fairly-airly' in MY-book ! _ (As that now-established standard could've just-as-well have been originally set at .1" -[2.5-times, still higher yet], and-yet still have as much logical-meaning behind-it !)



" Once I have done this as accurately as I can, I can report back here with the degree figures I obtain, "

____ I suggest that you take-note of all your degree-readings, with SEVERAL attempts at BOTH methods (of degree-reading efforts).



" and I will include lift. This may allow some of you to advise further. "

____ With it's max.lift-figures revealed, I'll then be able to tell you if it's possible that your D.cam is one of the factory-D.cam-models.



" reading some of the posts on this forum, I would be intrigued to find out how well dialled in - or not - this cam really is. "

____ It would seem that your previous searches for related posts, haven't turned-up all there is to be found on the topic. _ Have you completely searched-through all that turns-up, with: ' DESMO-camshaft ' entered ? - (Trying ' desmo cam ' , should of-course then find a less-restricted search-result.)
__ If your D.camshaft was actually manufactured by Ducati-itself, then I wouldn't expect it to be in very-great need of being dialed-in.



" is it possible to obtain offset keys for the singles, "

____ There was another thread that already covered this question, earlier this year !
Did you not-yet try searching: ' offset-key ' ? ... viewtopic.php?f=3&t=1302&p=9378&hilit=offset+key#p9378


Hopeful-Cheers,
-Bob

[Dave450]

Hi Dave

Factory figures are given at initial lift, which is an airy fairy way of checking things as the rate of rise is very slow. If you give me figures of 1mm lift with zero clearance I can look at the figures for you.

You set a zero clearance by placing a feeler in to take up the the clearance. At this point you may need to loosen up the closers to allow you to turn the engine over (Desmo's don't you just love em!). Mind you if you don't have the original springs installed, you will need to pull up the closing rocker hard and carefully place a feeler gauge to take up the clearance, not the closing clearance as well!. Without the springs you will also need to hold the closing rocker up when taking reading too.

At zero and 1mm lift you would be looking for figures of around inlet opens 52 degrees BTDC closes 76 degrees ABDC and exhaust 78 degrees BBDC closes 40 degrees ATDC. With lift around 12.3mm inlet and 11mm exhaust. That's a sort of average of figures I've taken from Imola Profile cams in Singles. You can work out the lobe centres if you want, but these figures work very well. This all assuming the cam is as described!

Nigel

Hi Nigel - that is very well explained, thank you! When I manage to find the time to dedicate to this, I shall report back, probably in a week or two. And yes, as you say, one assumes the cam is as described.

Dave

[Dave450]

____ Did he mention who the manufacturer of that D.cam was ?
__ Back throughout the '70s, I was in contact with sources who should've known, and I then never heard any tale of an "Imola" camshaft for any SINGLE-model.
I have heard 'tale' of Factory-made Red&White-D.cams made for racing 450D.engines,, BUT-however, it was made clear to me (back at the time, well-before the '80s) that the R&W-D.cam was intended specifically for the 350D.engine ! _ While the 'Gray & White' D.cam was the equivalent 'Special' DESMO-cam specifically intended for the 450-engine.
Does your odd D.cam have any similar paint-code (shown on it's threaded tip-end) ?
Can you provide all the min & max lobe-figures of your particular D.cam ?

Hi Bob - I don't remember Witt-Mann mentioning who made the cam. I bought it some time in the mid-1980s. I have looked to see if there was any paint code, but no, not even a trace. The information on the various race cams that you gave above is new to me.

I will try to obtain the lobe figures for you.

Dave

[LaceyDucati]

Hi all

The 1mm method is in my mind the best way to most accurately set the cam for repeatability and comparison. Yes it could be 0.020" or 0.100" to gain a steeper rate of rise than initial, but you have to set a standard and stick to it. Yes the figure has no actual relevance but it is much more pin point accurate. If you what to take actual opening/closing figures for comparison to other cams measured that way and Ducati cams, fair enough and I see the logic, but don't get all excited about the odd few degrees difference as it may not be real. On most cams I regularly use, I have been through various cams plotting the curve every degree and comparisons are made to those figures. Once I know a cam and as I have a good manufacturer I'm just interested in repeatability.

In fact timing figures and lift don't give the whole story anyway and wether the actual instance the valve opens is any more important is debatable anyway. The return pulse for an exhaust etc doesn't take place in an instance with the valve off the seat a micron! In my experience all the theory and calculations for things like exhausts and inlet lengths etc are only a starting point anyway and wether you put in 75 degrees or 80 degrees into your calculation is in fact fairly irrelevant in the big picture!

Much as some of you may not be great fans of Japanese bikes of the period and there methods, they did produce some very quick bikes, so I guess they knew a thing or too. You only have to look in a sixties K series Honda port to realise how crap Ducati ports are! One thing I have learnt is if you want a improve/change a Ducati don't keep looking in a Ducati engine, look elsewhere in engine design. I'm sure the Ducati factory has quite a few Honda engines in there development department, If they haven't they should have!!

A final note on cam timing and "dialing in". I always set cams to the nearest overall degree for consistency, but in fact playing around on the dyno gives some interesting results. Firstly I found that advancing or retarding 3 degrees from the manufactures settings made very little if any difference. Moving 6 degees did start to effect the power curve but not as much as one would think. Advancing the cam 6 degrees knocked about 1 bhp or so of the top end with little other difference. Retarding the cam 6 degrees left the top end much the same, but lost about 1.5 brake all through the rest of the curve. All these tests were carried out on a 350 race bike on the same day without other changes and fueling was checked thoughout. The timing was returned to it's original setting at the end to check repeatability. Moral of this story is most cam designers have good reason to recommend the figures they give and there is not normally great gains to be made by fiddling.

How this carries over to road timing, I don't know as I haven't tried as yet, my guess is the results will be similar. I would therefore say errors of two or three degrees are probably not worth worrying about and errors in excess of 6 degrees will probably have a major effect. One thing to note is my tests on Conti exhausts, original and various replica ones (all straight through) had a far more marked effect on the power curve on a tuned 350 road bike than these timing experiments.

Best Wishes Nigel

P.S The Imola cam that I found strangely came out of 450RT, the tunnel had been bored out and the cap sleeved. I do vaguely remember some grey paint, but it was mostly gone. Not at all sure how suitable that cam would have been in a standard RT head off road

[Dave450]

Hi all

The 1mm method is in my mind the best way to most accurately set the cam for repeatability and comparison. Yes the figure has no actual relevance but it is much more pin point accurate. If you what to take actual opening/closing figures for comparison to other cams measured that way and Ducati cams, fair enough and I see the logic, but don't get all excited about the odd few degrees difference as it may not be real. On most cams we regularly use we have been through various cams plotting the curve every degree and comparisons are made to those. As in fact timing figures and lift don't give the whole story anyway.

Therefore as to Wether the actual instance the valve opens is any more important is debatable anyway. The return pulse for an exhaust etc doesn't take place in an instance with the valve off the seat a micron! In my experience all the theory and calculations for things like exhausts and inlet lengths etc are only a starting point and Wether you put in 75 degrees or 80 degrees is in fact fairly irrelevant in the big picture!

Much as some of you may not be great fans of Japanese bikes of the period and there methods, they did produce some very quick bikes, so I guess they knew a thing or too. You only have to look in a sixties K series Honda port to realise how crap Ducati ports are! One thing I have learnt is if you want a improve/change a Ducati don't keep looking in a Ducati engine, look elsewhere in engine design. I'm sure the Ducati factory has quite a few Honda engines in there development department, If they haven't they should have!!

A final note on cam timing and "dialing in". I always set cams to the nearest overall degree for consistency, but in fact playing around on the dyno gives some interesting results. Firstly I found that advancing or retarding 3 degrees from the manufactures settings made very little if any difference. Moving 6 degees did start to effect the power curve but not as much as one would think. Advancing the cam 6 degrees knocked about 1 bhp or so of the top end with little other difference. Retarding the cam 6 degrees left the top end much the same, but lost about 1.5 brake all through the rest of the curve. All these tests were carried out on a 350 race bike on the same day without other changes and fueling was checked thoughout. The timing was returned to it's original setting at the end to check repeatability. Moral of this story is most cam designers have good reason to recommend the figures they give and there is not normally great gains to be made by fiddling.

How this carries over to road timing, I don't know as I haven't tried as yet, my guess is the results will be similar. I would therefore say errors of two or three degrees are probably not worth worrying about and errors in excess of 6 degrees will probably have a major effect. One thing to note is my tests on Conti exhausts, original and various replica ones (all straight through) had a far more marked effect on the power curve on a tuned 350 road bike than these timing experiments.

Best Wishes Nigel

P.S The Imola cam that I found strangely came out of 450RT, the tunnel had been bored out and the cap sleeved. I do vaguely remember some grey paint, but it was mostly gone. Not at all sure how suitable that cam would have been in a standard RT head off road

Nigel, your findings are very interesting, and thanks for sharing this information. I will bear this in mind when I get the actual figures, and it may end up that I just line up the dots and leave it at that, but I am still curious to find out what the valve timing is in reality.

I agree with you about the effect of Conti silencers on performance. The bike has much more mid range than with an unrestricted race exhaust, and less top end. The fatter mid range, and more eager acceleration compared to the stock cam, are great benefits on the road. It doesn't need to be revved hard out of slow corners or when passing traffic. It is surprisingly well behaved on the road with the race cam, 40 mm Dell Orto, slightly higher c.r, and with standard ignition timing, using a Lucas RITA system.

Dave

[Dave450]

Update on 450 race cam timing:

Ideally, I should check the timing with the engine on the bench, but this will have to do for the moment.

Checking clearance (1.00 mm lift, zero clearance): The figures I got so far were: inlet opens 40 BTDC and closes 86 ABDC; exhaust opens 65 BBDC and closes 52 ATDC. I am less confident of the precision of the inlet figures as the clock had to be mounted at a slight angle because space is so tight.

Degree readings at maximum lift:
Inlet: 114 ATDC
Exhaust: 90 BTDC

Perhaps Nigel and others can interpret these figures?

I can't give you accurate figures for maximum valve lift with the engine in the frame - my clock only measures to 10 mm. Measured without the clock, at valve, very roughly inlet 12 mm and exhaust 11 mm.

If this is any help, cam lobe dimensions are:
Inlet: 33.3 mm; Exhaust: 32.2 mm. I measured the standard factory cam lobes for comparison: Inlet: 31.00 mm; Exhaust: 30.25 mm. A few photos of the race cam are attached below.

Bob, I meant to thank you earlier for the link mentioning offset keys. I now know they are available if needed.

Dave

[Eldert]

Hi Dave

looks to me your cam timing is a little off . this is easely corrected by moving the lower gear a tooth and by moving the upper gear one tooth to . this gives you a change of 8.6 degrees .

i try to explain how to do it . the lower gear on the crankshaft ( if the dots are lined up ) the dot is in the 12o clock
position you have to move the gear on the crankshaft one tooth so the dot is in the 1o clock position .

for the upper camshaft gear when the dots are lined up the dot on the camshaft gear is in the six o clock position
you have to move this 1 tooth to so the dot on the camgear is in the 7 o clock position

have fun with it

Eldert

[LaceyDucati]

Hi Dave
Looks to me that those figures are Imola timing and lift, but hard to be absolutely sure without a good set of full figures. However as Eldert said the figures are out, I reckon about 10 degrees retarded, if you follow Elderts instructions that will give you a 8.6 degrees advance and get you where you want to be.

Advancing these cam timing figures will more than likely make little if any loss to the top end, but will probably improve the mid range noticeably.

Regards Nigel