Vincent Related David Tompkins Vincent at Daytona

[Bill Thomas]

Hi there Bill........ It's 92 x 100 so similar specs to the original just bigger........ I am careful to limit max rev's to 7000 on account of piston speed.......It feels like it will keep reving, but to be honest i shift at about just over 6000 as it has huge torque and just pooring on the revs seems unnecessary.

Greg, Is the Liner bit above the muff the same height, On the Terry Prince barrel ?, As standard,
Looks bigger in the photo ?.
I have a 92 Carillo piston, But have to get a barrel .
Cheers Bill.

 

[vibrac]

Compared to UK circuits (Silverstone excepted) Daytona is a different world! the first time I rode any track was at Silversone in the early sixties and I was completely lost without any visual clues as to where the track went now its even worse (I blame the trolly F1 racers) . Greg is right that sort of flat out track is not one where the Vincent Single would normally shine. At Cadwell however in the days when owners actually rode Vincents hard and corners abounded (and still do) , the Comets often presented their rears to the twins. leading at the time to intense discussions.

 

[greg brillus]

Hi there Bill the liner is the same height but it is much wider.......More suface area, to seal better........I don't support this theory. I did lap the liner into the head recess before the liner was installed into the muff.........Neal Videan supplies some of these parts, I could ask him for you if he has anything........I have a new spare liner in case my one suffers any issues. Racing is great fun.........asside the cost and time........Pushing a bike and yourself to limits far beyond what you would ever do on the road is something else, especially when you have some close competition..........The twin in my picture left was simply great, you could hug someones back wheel diving into a corner, then out turn them driving out.........This ability to corner so well is something my newer Norvin single does not do as well........despite jacking the rear of the bike, and i could lower the front just dropping the yolks through the staunchions. It is all experimental, and you risk making the bike unstable........If I can't get a good result, I may just pull it down and re build the bike back up as a true Vincent........ Some of those straights on that track look like you could just keep accelerating if you had the power and gearing......... Not something many old bikes have.

 

[Bill Thomas]

Thanks Greg, I did Racing for 17 years , So I think I have had enough FUN ?.
Going past a load of Blokes is a real Buzz,
One of my best was an hour highspeed trial, Cadwell park, I lapped the second bloke twice,
Can't tell you how many times I went past some of the others !,
But I could only get a first class award, It was not a Race.
I was going fast for the first half hour, Thinking there was a Velo that was a lot faster than me,
Thought he should have got me by then ?,
Turned out he didn't start !!!.

I don't really want a Nikasil Barrel, And I would like to use a standard muff with the standard studs,
I will have to save up a bit and talk to Conways,
I have spent a lot, For me !, Last year on these Cases that were already bored out and other bits,
I thought I was winding down, 75 in March !, But I saw these cases and could not resist,
I am just a Silly Old Sod !.
Cheers Bill.

 

[ericg]

Hi Bill,
If you still want to go big bore, you can't use standard studs with a Conways 90mm kit, as far as I know.

 

[Bill Thomas]

Hello Ericg. All I have is a 92 mm Piston and C/Cases with a BIG hole !,
Looking at the T/Prince set up, I thought I could get away with a Standard muff and studs,
And grind a flat on the studs where the liner top flange would be ?.
Just a bit of Fun ! ?.
Cheers Bill.

 

[greg brillus]

Bill the issue with using a standard type muff bored out that large, is the holes end up right next to the edge of the bore........I havent seen it myself, but have been told these will simply crack in service. I know Neal Videan has special alloy muffs in stock that have much more meat around the through hole area.........These are a casting only and need to be fully machined on all surfaces/holes.......I think on all these larger cylinder assemblies, they use a 2 piece through stud, the lower half has a 10 mm shank with a fine M10 thread at the top for the upper stud to screw down like an extension. The threads on either end are standard sizes.

 

[Bill Thomas]

I have had a good look and if the liner is 3 mm thick , Same as standard,
I think it should leave enough,
I have in the past made the the head and liner and muff all touch at the same time,
If, As I think you have said ?, You like a gap between head and muff ,
I can see how it would crack ?,
There is always a risk with these things, I have took a few in the past ! ,
Who knows, If it works, I could maybe do a 102 stroke and would get a 6 ????? cc ,
Then it would be Soo Fast, I could sell one of my Twins ??.
Welcome to my Dreams .
Cheers Bill.

 

[medat727]

I still find it difficult to believe a 500 Vincent is that competetive against other 500 race bikes of the era........Most other high end Brit singles put out more than 40 HP. The ESO speedway engine I ran in mine before the engine change put out 45 straight out of the box. It is very difficult to extract bigger HP from a single.......Mine is a 665 cc putting out 48.2 HP and still does not have enough especially in the unlimited class.........I sent my head away to a friend who is installing bigger titanium valves and modifying the seats and ports.....we are changing the seat angles to 50 Degrees and running beehive springs........ratio the rocker assembly...... I am aiming for 0.550" lift larger inlet valves and smaller exhaust.......We have worked out that basically the valve train in a Vincent is quite poor for developing big HP figures ......the use of roller symetrical cams and ratio rockers is the answer, but unless you have a better oil pump system, you will be waisting your time, Oh and stronger pushrods and everything else to go with it........Upon disassembly of my head recently, I found the valve stem collars were very worn.........The rockers themselves were fine, but the collars had not........possibly from not being hard enough, also I am going to increase the flow of oil to this area of the head much more once the modified head comes back.......My head is one of the latest types of the 600 kits that Terry was selling........this with the chambers and ports fully CNC'd.......Apart from matching the port to the inlet manifold, I had done no other mods to it........It was a good starting point, but now the fun begins........Who knows if it will survive.

Greg, the Class C Foot shift class is production-based machines of the period that existed up to and including 1951. My chief competition comes from a pre-war Norton Manx ridden by Alex McLean who is a rare talent indeed, the David Dunfey motor combined with a serious effort to lighten the bike has made the machine a superior mount. When I run against Alex’s modern Manx in the Classic Sixties 500 class which is my bump up class, I get my head handed to me although I do have success against the Triumph Daytona’s and lesser riders on late model Manxs.

I too have a later generation Terry Prince head that is slated to be used in an upcoming race engine, it will have to be modified to run as a 500 along with addressing other issues so I’m quite interested in what you are doing with yours. I’m curious about your decision to go with 50 degree seat angles, I believe stock Vincent valves are 30 degrees which give good low lift flow but don’t seal as well as a 45 degree seat, 50 degrees from what I read really only comes into play with high lift flow?

 

[ericg]

I have had a good look and if the liner is 3 mm thick , Same as standard,
I think it should leave enough,
I have in the past made the the head and liner and muff all touch at the same time,
If, As I think you have said ?, You like a gap between head and muff ,
I can see how it would crack ?,
There is always a risk with these things, I have took a few in the past ! ,
Who knows, If it works, I could maybe do a 102 stroke and would get a 6 ????? cc ,
Then it would be Soo Fast, I could sell one of my Twins ??.
Welcome to my Dreams .
Cheers Bill.

92 x 102 = 678cc