Terry Prince 1350/1360 on the dyno

This is Terry's race bike, with mostly the same components as in my 1360 engine. Although mine runs very strong on two 41 mm Dellortos, this result has me thinking about fuel injection. Hobot could do some sideways wheelies with this.
Glen

I'm sure Terry's bike is awesome. And I know that Terry is a top Vincent geezer. But surely, that has to be an opermistic dyno...?

Even if it was a 15% optimistic Dynojet number(it's not a dynojet), it is still huge power. I have found Terry to be a somewhat understated individual so likely the number is correct. Afterall, Horner Bros built their first successful 1300 racer using Terry's stuff and then went on to build other versions which dynoe'd similar amounts of power to Terry's. I imagine the fellow on the Ducati 1198 who was beaten by the Horner Vincent at the Battle of the Twins would not doubt the horsepower numbers.

The real dyno test will be Bonneville and Lake Gardiner.

Glen

Glen,

Might you know the bore, stroke and IN valve size in Terry's engine?

Have you had yours on a dyno, and if so how much power does yours make?

Terry's engine is 92 mm bore and 102mm stroke, identical with mine in displacement. Most components are also identical, however his engine runs 13 to one compression, fuel injection and methanol fuel. Mine is a street machine and runs 10.5 to one compression , 41 mm Dellorto Pumper carbs and premium pump gas. I have not had my engine on the dyno yet. It will produce considerably less Max power than Terry's, though still likely somewhere north of 100 rwhp, according to Terry.
Due to the light weight of the bike and the instant power delivery, I find that it hits harder than my 162 bhp Triumph Daytona.
Brutal is the best description of how the Vincent 1360 accelerates.
Glen

I can't even afford to read this thread let alone imagine what one of those engines cost. :mrgreen:

I've not worked it all out, but probably the costs are similar to building a real hotrod Norton engine, ie Full auto head further modded by Jim, billet cases, race crank, alloy barrels and tti trans , etc.

Glen

swooshdave said:

I can't even afford to read this thread let alone image what one of those engines cost. :mrgreen:

Click to expand...

Your funny swooshdave I'm still smilin' from that post ....nice to know this stuff's out there though.

worntorn said:

Terry's engine is 92 mm bore and 102mm stroke, identical with mine in displacement. Most components are also identical, however his engine runs 13 to one compression, fuel injection and methanol fuel. Mine is a street machine and runs 10.5 to one compression , 41 mm Dellorto Pumper carbs and premium pump gas. I have not had my engine on the dyno yet. It will produce considerably less Max power than Terry's, though still likely somewhere north of 100 rwhp, according to Terry.
Due to the light weight of the bike and the instant power delivery, I find that it hits harder than my 162 bhp Triumph Daytona.
Brutal is the best description of how the Vincent 1360 accelerates.
Glen

Click to expand...

What size are the valves?

worntorn said:

I've not worked it all out, but probably the costs are similar to building a real hotrod Norton engine, ie Full auto head further modded by Jim, billet cases, race crank, alloy barrels and tti trans , etc.

Glen

Click to expand...

No matter how much money you could throw at Jim, which would be considerable, could he find 160 hp in a Norton engine. Well, he might but I bet life expectancy would be measured in seconds. :mrgreen:

Terry never built a 160 brake motor. my mates 1200 RTV is half that..he talked about 100 bhp with fuel injection .

John, to compare the RTV 1200 Vincent to Terry's current 1360 ccracebike, which produced 165.2 rwhp on dyno, is a bit like comparing a Commando to a 2015 gixxer 1000. Though Terry had some good ideas with the RTV, it was very early days
in his experimentation. Everything that matters has been changed then changed again several times. Think modern day Burt Munro. Burt started with a bike that had perhaps 15 HP and went 60 MPH then modified it again and again until it broke 200 MPH. Terry is doing a similar thing, but started with a bit better candidate, the Vincent engine which is no slouch in stock form.
Terry bought the bike as a stock Rapide about sixty years ago when he was 17 years old and still living in England. It has had many forms over the years.

Dave, I suppose by your measure maybe the cost isn't quite so outrageous, so thanks , I will use your point as my rationalization going forward :mrgreen:

Re valve size. My engine uses standard Vincent sized valves, which are quite large, 2" for intake and 17/8" for exhaust if memory serves. Phil Irving liked to use a large valve and low lift, which made hotrodding this component easy , just add a bit of lift. Standard lift for a road going twin is just. .312" which jumps to. 343" for Irvings hotrod "Black Lightning " cams. Terry Prince went much higher , all the way to .460" with his MK4 race cam. Fritz Egli Jr. used the Mercedes Formula One Race Team's cam development program to design Terry's MK5 cams. The program said that with 6500 rpm as the intended Max output rpm, there was no point in lifting the valves more than .440 intake and. 425" exhaust, so that is what the MK5s do. Both Terry and I have these MK5s installed and they work extremely well. A nice lumpity lump no stall idle, then good controllable power just off idle, then anywhere above 2000 rpm, hang on!
I'm not sure what size valves Terry is using.

Glen

Glen,

Thanks for sharing all the build details. The reason I asked about the valve size was because I wanted to back into the HP number by correlating only airflow potential from a given IN valve to power potential (assumes high compression, optimum cam and pipe). So, considering only the valve size (2.0" dia) and using literature relationships for maximum power potential from a given airflow, the following estimates were made.

A 2.0" valve in a hemi chamber (chose hemi chamber because it has higher flow potential than wedge) flowing at theoretical potential would pass ~ 200 cfm at 10" WC. In turn, this airflow in a 2 cylinder engine has the potential to support ~ 172 HP on gasoline. On alcohol the HP potential is higher (combination of higher energy content from the large alcohol charge and tolerant of higher compression than gas) and could be 240 HP. Applying a large drive train loss of 10% suggests that there is RWHP potential on gas and alcohol of 155 HP and 216 HP respectively.

In light of the above, the dyno numbers Terry cited certainly appear to be well within the realm of reality for a well prepared race engine realizing the full airflow potential of a 2" IN valve. In his favor, the fact that he has FI, and presumably has large throttle bodies, serves to minimize flow losses that occur with carbs. His result suggest that airflow is well below entitlement, which would not be surprising given that the Vincent head/induction system was likely not optimized for flow.

One specification associated with the build that puzzles me is the low valve lift of 0.440". I assume you have quoted valve lift, not cam lift? Is that true?

That's correct, .440" is valve lift.
I should point out that these heads appear outwardly to be the same as conventional Vincent heads, but are actually different in almost every way. Inlet port size on a standard Vincent head is 28mm, Terry's are at 42 mm (mine are at 38 mm)and very different in shape from many years of trial and error plus flow bench testing. Additionally, the combustion chambers are twin plug bathtub shaped with large squish vs single plugged hemi with no squish for a standard Vin. Exhaust ports are filled in at bottom to form a sideways D for exhaust reversion prevention.
He has also made improvements to the rocker bearings(doubled the surface area), improved the rocker oil feed connection to a leak proof design and added 25 % more fin area for cooling.



Glen

worntorn said:

That's correct, .440" is valve lift.
I should point out that these heads appear outwardly to be the same as conventional Vincent heads, but are actually different in almost every way. Inlet port size on a standard Vincent head is 28mm, Terry's are at 42 mm (mine are at 38 mm)and very different in shape from many years of trial and error plus flow bench testing. Additionally, the combustion chambers are twin plug bathtub shaped with large squish vs single plugged hemi with no squish for a standard Vin. Exhaust ports are filled in at bottom to form a sideways D for exhaust reversion prevention.
He has also made improvements to the rocker bearings(doubled the surface area), improved the rocker oil feed connection to a leak proof design and added 25 % more fin area for cooling.
Glen

Click to expand...

I did a little diddling regarding the estimated port speed of your engine and I think your port size of 38 mm is perfect to achieve optimum port speed.

I asked about valve lift because 0.440" is really low lift for a 2" valve in an OHV engine. A lift of 0.440" is only 22% of the valve dia, which is more typical of the lift employed on a flathead engine (poor breathing relative to OHV), where 40% of the valve is masked, flow tends to be more across the valve than around it, and flow maximizes between 20-25%. At a valve lift of 25% the curtain area equals the valve area, thus this is usually the minimum lift employed in an OHV application, but more common is 30% and in NASCAR I believe flow increases up to 35%.

Is there some fundamental reason or limitation of the system that requires such a low lift? Too much x-over flow between IN & EX in the bathtub? I can't imagine the airflow potential of a 2" valve is realized when lifted 22% of the valve dia, but I don't know the head or port so possibly it is?

As always I suspect there is much more to the story, so I'll stay tuned for your response.

The MK5 cam from Terry Prince is the first computer designed cam for Vincents, as far as I know. It came about after Terry had a discussion with his godson, Fritz Egli Jr., son of the famous Egli frame designer. Fritz Jr. was lead engineer on the Mercedes Formula One racing team until recently and as such had use of the team's cam development program, a very expensive piece of software.
Fritz offered to use the software to design a high performance cam specifically for the stretched Vincent top ends that Terry builds. Terry gave Fritz Jr. all of the relevant data and Fritz plugged the numbers into the program. The result was this MK5 cam which both Terry and I have used on our 1360 bikes, but not many others have. I believe Mal Hewett also uses the MK5 on his Vincent racebike which just set a new speed record on Lake Gardiner.
Some of Terry's previous cam designs (he has tried a great many) used a lift at valve figure as high as .50" however the Mercedes F1 program said that there would be no improvement in breathing beyond a lift of. 440" for the rpm range and other parameters given, so that is where the. 440" number came from.

The MK5 cam when tested on dyno far exceeded power output from any other race cam Terry had tried. He was at first unwilling to sell them to me for street use, thinking they might be unsuitable in the lower rpm range. After running his racebike for awhile with the MK5s installed he decided they would be tractable enough at low rpm for street use. It turns out that the bike idles quite well, though it is a lumpy idle, and pulls away easily with very light throttle. From 2000 rpm on up it pulls extremely hard and throttle response in general is quicker than I am accustomed to on either my litre sportbike or the vintage bikes here.

Glen

Regarding the head you are running, have you ever seen (or measured) the airflow curve as a function of valve lift, and if so, does airflow maximize by 0.440" lift?

Apologies for prying into every nook and cranny of your project, but every tidbit helps me better understand engine performance. Thank you.

No apology required, I appreciate the interest, just wish I had more detailed info.

When I ordered the top ends from Terry he told me that the heads would not be cast until he had made changes to his existing patterns, which are an evolution of high performance Vincent heads he designed in the 1980s. He was in the midst of flow testing several new prototypes when I made the order. The best shape/design would be the type chosen for a batch of fourteen heads he planned to have made up, two of which were for my engine.
Terry has reconfigured the 1980s design several times over the years, then tested the results on his own bike both on dyno and on the salt. Around 2007 he sold smaller sized set of these heads (he has 84 & 92 Mm sizes) to the machinist/motorcycle racer Steve Hamel who wanted to revisit Rollie Free's Bomneville record of 1949. Steve wanted to see if he could break Rollie's record, but do it on pump gas rather than the alcohol fuel Rollie's Lightning ran. Steve revamped Terry's high performance heads considerably and upped the output of his 998cc machine to over 100rwhp then with further mods 120 rwhp. Here is his bike at the 100 HP stage. https://m.youtube.com/?#/watch?v=z6SpCobouDc
He did break Rollie's record with that bike.
This made Terry take notice, so he incorporated some but not all of Steve's modifications in another new design, the one he was busy flow testing when I made my order in early 2010. I received the heads in early 2011. Terry did not incorporate all of Steve's changes as Steve's is a/Bonneville racer, top end only type engine and Terry wanted to keep a strong level of midrange power with his design. I can attest to the fact that he got that right.

So all of the R&D has been done by Terry Prince and Steve Hamel , some of it going back to the 70s. That's what make these top ends relatively good value, it's not so much the foundry work and machining which goes into a current set as it is all of the expensive R&D that went on to get here., much of it trial and error I'm sure.

Bonneville 2012 Steve Hamel Vincent ;

https://www.youtube.com/watch?v=xZHsKhi-KyI

https://www.youtube.com/watch?v=z6SpCobouDc

No, No, you are looking at it wrong. With the valve at .440 lift, the area around the valve available for flow is 2.76 sq" on a 2" circle, slightly less if you want to take it at the contact point with the seat. With an 1.3/8" port behind that valve, the cross sectional area is 1.48sq". So you can see the valve at .440 lift has the capacity to flow far more than the port will allow. Most likely the valve would be flowing max port flow at about .380" lift.