I need a drawing of ET84, exhaust nut
- Thread starter johnmead
- Start date
Glen,
I too have modified the Renwick cams a bit. The great part about Johns cams is that they do not drop quickly. If you are at 7000, 7500 or 8000, the power is about the same. The power is lower than peak, but it is pretty reliable, so if you are racing to the line it does not shut off.
I know that Terry calls the MK4 his race cam. I also know that Mal Hewit used the MK5 in his Bonneville engine. I know that the MK5 can used the radiused followers, but I am surprised at the 12 hp figure. I have both cams plotted, but they were not scanned in so I cannot put my hands on them. Terry will certainly provide the information he has to anyone that is interested.
David
I too have modified the Renwick cams a bit. The great part about Johns cams is that they do not drop quickly. If you are at 7000, 7500 or 8000, the power is about the same. The power is lower than peak, but it is pretty reliable, so if you are racing to the line it does not shut off.
I know that Terry calls the MK4 his race cam. I also know that Mal Hewit used the MK5 in his Bonneville engine. I know that the MK5 can used the radiused followers, but I am surprised at the 12 hp figure. I have both cams plotted, but they were not scanned in so I cannot put my hands on them. Terry will certainly provide the information he has to anyone that is interested.
David
Bruce, I'm not sure what modifications Roy made to the Renwick cams. He just mentioned that they were "heavily modified"
David, the 12 hp figure is from memory and could be incorrect. The number mentioned was from Terry's 1360 engine running alcohol at 13 to one so likely it is a larger number than if the same cam change was done on a 998 cc motor in a lower state of tune.
I believe Peter Volkers uses Terry's MK2 Lightning cams in the bike he used to terrorize the Martials @ the IOM. Terry mentioned that Peter's testing of those cams showed a continued HP increase thru to 6500 RPM whereas engines using regular Lightning cams show max hp and 5500 then drop off as RPM increases from there.
His Mk2 lightning cams sound like a good choice for a fast road bike. Hope his health improves, he has certainly improved the health of many Vincent engines!
Glen
David, the 12 hp figure is from memory and could be incorrect. The number mentioned was from Terry's 1360 engine running alcohol at 13 to one so likely it is a larger number than if the same cam change was done on a 998 cc motor in a lower state of tune.
I believe Peter Volkers uses Terry's MK2 Lightning cams in the bike he used to terrorize the Martials @ the IOM. Terry mentioned that Peter's testing of those cams showed a continued HP increase thru to 6500 RPM whereas engines using regular Lightning cams show max hp and 5500 then drop off as RPM increases from there.
His Mk2 lightning cams sound like a good choice for a fast road bike. Hope his health improves, he has certainly improved the health of many Vincent engines!
Glen
Bruce,
If you are grinding cams in the garage it is difficult to keep the lobe centerlines accurate. If you are trying to get out pits from stelliting, the inclination is to keep grinding, but every time you do so the cam timing can change. The all important opening and closing events can change, without much ability to control them. Finally, it is easy to get the dreaded dip before opening or after closing which can be hard on the vavle gear.
If you have a cam machine, it is much easier to engineer the oversize master and dictate all of the openings, closings, centerlines, lovely ramps and overlap. You can see the difference in scale of the master and the cam. The more your home grinder compromises the difference, the harder it is to control the output. This is just a random photo,but it one lobe only and two lobes requires a more complex set up.
David
If you are grinding cams in the garage it is difficult to keep the lobe centerlines accurate. If you are trying to get out pits from stelliting, the inclination is to keep grinding, but every time you do so the cam timing can change. The all important opening and closing events can change, without much ability to control them. Finally, it is easy to get the dreaded dip before opening or after closing which can be hard on the vavle gear.
If you have a cam machine, it is much easier to engineer the oversize master and dictate all of the openings, closings, centerlines, lovely ramps and overlap. You can see the difference in scale of the master and the cam. The more your home grinder compromises the difference, the harder it is to control the output. This is just a random photo,but it one lobe only and two lobes requires a more complex set up.
David
Didn't PEI use a tap grinding machine and a similar oversize master? I gave Bert Weisz a MK2 cam and I believe was going to make his own during his night shift at the Ford works. I never remembered to ask how that went. I might still have the long MK2 cam with a lot of wear from an ET43 wrapping around it, anyone want it?
Glen,
I just contacted Terry and he has one set of the MK5 cams available. I ordered them along with a set of his radiused lifters. They should be here in a week or so and I plan on using them instead of the MK4s I have. Terry says that the MK5s are easier on the valve train and produce the same power at about the same rpm as the MK4s.
I will install them as is and later try a set of re-ratioed rocker arms to get more lift and duration as the lift is less than the MK4s.
John
My understanding from talking to Terry at Kanab last year is that the MK5s make considerably more power at high RPM than the MK4s do. He said the MK4s were an older design of race cam that was found to be pretty effective but the MK 5s were the ones to get for max power , or words to that effect. I recall the 12 hp figure but that might have been VS his MK2s, I was also considering those.
Anyway, I like the idea of using the Mercedes F1 cam development program to come up with a cam profile. It was the use of this program that showed there was no benefit in lifting those large Vincent Valves higher than .440, hence the lower lift than MK4s.
And I just ordered an extra set of the MK5s plus followers from Terry , supposed to be here in a week or so. He said these were the last he has and isn't planning to make anymore parts. Must have dug deeper in the parts bin, we can't both have the last set!
Here is what I like- Radical cams and a rock steady tickover. something that is essential on a Road bike (mine, not Mal's) that will get used for touring and inevitably get stuck in city traffic.
The midrange sounds pretty healthy too. And 162 up at Bonneville without fairing ain't shabby!
http://youtube.ca./watch?v=ibMu1dBf894
Glen
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