• Welcome to the forum website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Online Forum Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this forum website.

    If you have previously registered to use this forum website, you should log in now. CLICK HERE.

    If you have never registered to use this forum website before, please CLICK HERE.

identifying cams

redbloke1956

Well Known and Active Forum Website User
Non-VOC Member
Hi again to all,
Can anyone tell me how to identify my cam/s i.e. are they standard or Mk1 or Mk 2
Can anyone tell me, if they are standard cam/s, are there cam/s of increased performance that can be fitted without further modification to the engine ( I am thinking of a TPV top end conversion some time in the future)
Thanks in advance.
Kevin
 

Len Matthews

Well Known and Active Forum Website User
VOC Member
The majority of camshafts are stamped 1,2or3 either at the lobe end or sometimes in the recess at the pinion end. Problem arises if a worn cam has been built up and reground to a different profile. The Mk2 cam will certainly enhance the performance but it's necessary to shorten the Lower Valve Guides in a standard Cylinder Head. Can't advise regarding a TPV Cyl. Head ask Mr. Prince!
P.S. Mk1 cam was the original, Mk2 for racing, Mk3 same as original but with so-called quietening ramps. I could never tell the difference noise wise!
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Gary Robinson modifies cams to a spec by Ian Hamilton, called "105's" (after the overlap figure, I think). I have them on my Shadow. They work very well, although whether better or worse than Marks I, II, and III, not having done "controlled comparisons" I can't say. Suffice to say it'll do 100 easily sitting upright, cruises easily at anything between 50 and 90, and is perfectly happy to dawdle around town. Who needs more?
Hi again to all,
Can anyone tell me how to identify my cam/s i.e. are they standard or Mk1 or Mk 2
Can anyone tell me, if they are standard cam/s, are there cam/s of increased performance that can be fitted without further modification to the engine ( I am thinking of a TPV top end conversion some time in the future)
Thanks in advance.
Kevin
 

davidd

Well Known and Active Forum Website User
VOC Member
With all of the performance cams you have to modify your engine. You will have to check that the lobes do not interfere with the exhaust lifting mechanism abuttments and often you have to grind out material in the head for increased lift. This is true of the 105 cams also. I know of at least one very unhappy owner who did not check the clearances.

The MK2 is known for performance with a straight pipe. Ian Hamilton designed the 105 to be a MK2 that would work with a silencer, so the differences are probably noticeable, but not dramatic. The 105 refers to the Lobe Separation Angle or LSA and I believe a MK2 has an LSA around 97 or 98.

David
 

A-BCD

Well Known and Active Forum Website User
VOC Member
The '105' cams are Mk II with reduced overlap, but the 105 refers to the fact that you time them with inlet valve at maximum lift 105 degrees ATDC.
 

davidd

Well Known and Active Forum Website User
VOC Member
That would surprise me. I have a 105 that Gary Robinson welded a cam wheel on and the gear wheel is marked and Max lift is at 88 degrees ATDC. The LSA measures 105. I must admit I am not an expert on cams, but max lift is usually not an event that cam designers use as a reference event.

David
 

A-BCD

Well Known and Active Forum Website User
VOC Member
I wrote up about these in MPH642 July 2002 !! This is what I said:

"I timed the inlet as close as I could to 105 degrees ATDC at full lift as recommended by Gary. I then clocked the valve timings and got these results:

INLET OPENS 47 BTDC INLET CLOSES 76 ABDC
EXHAUST OPENS 76 BTDC EXHAUST CLOSES 47 ATDC

EXHAUST MAXIMUM LIFT 102 BTDC.

So all in all, very symmetrical !! As Gary's cams are very consistent, you would probably be quite safe to time them with inlet opening 47 BTDC, you can always check the position of maximum lift."

But to quote Ian Hamilton himself, from MPH 558 July 1995: "to time the cam you need to find the position of peak lift. This should be 102 ATDC for the inlet and 102 BTDC for the exhaust. The figure of 102 is nominal and can vary between 102 and 105.
For those that want the total picture, the inlet opens at 44 BTDC and closes at 80. The exhaust opens at 76 and closes at 44. These figures correspond closely to the 80/40 cam suggested by A. G. Bell as optimum forr a 300 degree duration cam."

Gary Robinson supplies these as 'Hamilton 105 cams' and says to time them with the inlet valve at peak lift at 105 ATDC. I believe Ian's theory was that this is the point of maximum piston speed, therefore you should get the maximum charge into the combustion chamber.

Cheers, Brian
 

davidd

Well Known and Active Forum Website User
VOC Member
Brian has a better grasp of the history of the 105 cam than I do so I will defer to him. I am left with the puzzle that the Robinson 105 that I have has the inlet open at 48 and the peak lift is at 92. This is measured when the "split" is at TDC Ex as opposed to the timing marks, which would advance it another 4 degrees if the pinion is welded on in the correct position. I am not near the shop so without a double check I must assume the error is mine, but thank you to Brian for having the data at the ready.

David
 

vibrac

Well Known and Active Forum Website User
VOC Member
I have never worried about opening and closing points of a cam what the heck if its 10 thou or 20 thou off the seat at a point that is hardly measurable I am a great beliver in going for equal opening of both valves at 6 degrees BTDC thats where it matters I timed the single and the twin racers like that and the results are history,just to underline the point I also timed my trials Comet like that without even knowing if they were 1,2 or 3 cams and she pulled like a 650 panther so my guess is they are MK1.
Incidentally if you have gone to the bother of setting up dial guages on your valves just be amazed what small movements of the adjusters will do to your theoretical 'opening figures'. Now go figure what happens after a short run.
 

Howard

Well Known and Active Forum Website User
VOC Member
It's a long time since I timed cams on a Vin, so I can't say exactly how I did it. I remember books and sketches and dial guage etc etc, and I'm sure I timed them based on best compromise of opening and closing points, and front and back cylinders. I do know it was always a compromise, because as Vibrac points out theoretical figures were impossible to duplicate.

My question in this thread is, how do you set the point of highest lift? Surely there are several degrees at the top of the cam lobe where the lift is constant, a graph of the valve opening (time vs lift) will have a flat top, not a point.

H
 
Warning! This thread is more than 12yrs ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.
Top