Mark. III Camies in `53 Shadow - What is right timing?

davidd

davidd

Well Known and Active Forum User
VOC Member
Bruce,

Designing and measuring are two different things. Andrews sold the Vincent cam design to Megacycle, but if you sent either one your own Vincent cam and asked them where the inlet opened they would have no idea and no way of telling you other than installing it in a Vincent engine and degreeing it. I mention this only because you cannot hand a Vincent cam to a modern cam maker and expect them to say anything enlightening about the design never mind tell you where the major events occur. I can weld up a cam and they can copy it, but they will not be able to provide me with any data.

David
 
A

A-BCD

Well Known and Active Forum User
Non-VOC Member
This is the plot I did over 30 years ago, I assumed they were Mk III cams because they appear to have a quietening ramps. Equal lift is .100" at about 4 degrees BTDC. These were not new, you can see that the inlet and exhaust have different maximum lift !!
camshaftplot.jpg
 
bmetcalf

bmetcalf

Well Known and Active Forum User
VOC Member
Again this is from 28+ years ago, but I was led to understand that George E. worked with Andrews to design it, taking the followers into consideration and not just copy the existing profiles. Of course it may have been some of George's hyperbole. Megacycle very likely did just buy the design, masters, or CNC program and is as you say.

Ron Vane came through town about that time and we went to the Andrews works and they had a discussion of cams for his blower motor with long durations and short overlaps (that I only half listened to), so it reinforced my above impression.

davidd said:
Bruce,

Designing and measuring are two different things. Andrews sold the Vincent cam design to Megacycle, but if you sent either one your own Vincent cam and asked them where the inlet opened they would have no idea and no way of telling you other than installing it in a Vincent engine and degreeing it. I mention this only because you cannot hand a Vincent cam to a modern cam maker and expect them to say anything enlightening about the design never mind tell you where the major events occur. I can weld up a cam and they can copy it, but they will not be able to provide me with any data.

David
Click to expand...
 
S

Sebastian Huber

Well Known and Active Forum User
VOC Member
Thanks A-BCD, this allows me to compare.
I like to follow this discussion where theoreticaly basics brings me 30 years back to Institute of Technology at University.
 
T

Tom Gaynor

Well Known and Active Forum User
VOC Member
Thanks, Sebastian. I have a good Bavarian friend, Reinhardt Neumair, who races a Manx Norton. When I retired, he was leading me in the "European Classic Racing Broken Collar Bone" championship. I last saw him in A & E at Chimay. He had just broken his for the 15th time, I was catching up, I had thought, with my 3rd...
Remember two things:
Firstly, PEI designed the Mark II, Lightning, Rollie Free, cams "by eye". Designing cams, taking into account follower geometry, by manual calculation, is a BIG job. Few "oldtime" cams meet modern standards, although they often work very well. Details of how the Lightning cams were "designed" are in his autobiography. They had intended to have it done by a cam design specialist but ran out of time.
Secondly, the timed breather was dropped for the Series D. This was probably NOT because the timed breather was 100% satisfactory... Opening up the slot with a file to extend the timing helps. But a D breather, I believe, works better.
Incidentally, my enthusiasm for the "equal lift" method comes from my discovery that my 90 mph Rudge Ulster cam is equal lift (EL) at 4 degrees, my Manx Norton cams were EL at 4 degrees, my factory Honda race (HRC) cam was EL at 4 degrees, and my Gary Robinson 105 (a Vincent Mark II with more overlap) cam was also EL at 4 degrees. And according to Neville Higgins, so is the Terry Prince TPV cam. Must mean something...

Good luck anyway. And I hope your wife enjoyed her dinner as much as you enjoyed your temporary freedom from matters domestic...
 
Last edited by a moderator:
S

Sebastian Huber

Well Known and Active Forum User
VOC Member
Thanks Tom,
yes, last Friday evening was great.
Advices from an well versed guy makes life easy!
I worried about the question how to get information who could help before I decided to become Vincent driver but see that this forum works great due to people like you who passes experience and knowledge.
I succeded in timing valves and breather assembled engine and bike and had first rum on Saturday. Acceleration and speed is perfect (reached again nearly 100 mph after half a mile runin - engine keeps dry - is not new/ haven`t been reworked).
Planed to leave for FIVA-Rallye at Brands Hatch end of next week!

I should know Reinhardt because I go sometimes for VFV Histroic Races - as a visitor because I didn`t succed since decades to bring my Rudges (500 Ulster and 350 Replica) back on the road.

Thanks, keep well
Sebastian
 
Top