Who's Vincent/Hrd has the most power?

[Monkeypants]

on ratioed rockers etc. John, if you want higher lift it would be much easier just to use the mk 4 cams you started with. One of the things learned from the Mercedes F1cam developmeht program was that there is a point of diminishing returns for valve lift and also a point of no return whatsoever.. The mk 5s are a little lower lift than the mk4s because the program determined that there was no advantage in lifting the big Vincent valves beyond .440 (memory on the number, cant find the graph right now)
To put this in perspective, Irvings mk 1sgive .312 lift at valve, his mk 2s give .343 , Terry's mk 2s something like .370, mk5s .440 and mk 4s even higher.
So ratioed rockers with Vincent mk 2 s might be approximating mk 5 total lift? As Greg mentions, higher lift = higher valve train wear, so not much reason to go there if there is no power advantage. The mk5s took Malcom Hewitt to 162 mph at Bonneville.

 

[davidd]

John,

The folks that I know that have done it are Ken McIntosh, John Renwick, Ian Boyd and Lindsay Kyle. There are others, but I think that Glen has outlined the issues well. I think my cam goes to .478, but I was unaware of the rules, so it still makes good power!

David

 

[johnmead]

Hi there John, well you could try the rocker set up that John Trease here in Australia has done to a worked Comet engine using 1.6:1 rocker arm ratios.....this works very well, but the normal type of cams and followers won't last.....must use roller tiped solid type cams/followers and a much improved full pressure oiling system to cope with this set up......mind you, this engine puts out over 58 HP Greg.

Greg,
Can you provide me with contact information on John Trease. I would be interested in getting information on his cams and valve gear. A couple of years ago I came across information on Vincent roller cams made in the 1960 by K&H. They used rollers off of Harley XR750 listers and the cams profile was a XR750 race profile. I offered to buy the information and remaining parts off of the current owner of the K&H company but he doesn't want to sell.

John Mead

 

[mercurycrest]

Due to my inexperience, I am not able to think of a way to ensure the proper alignment of the offset. How would you do that?

It;s easy with a jig Bruce
35-40 years ago we didn't have the luxury of Terry's cams or computerized programs, so I used my friend, Pat Connoly's cam design... He got a 650 BSA to go 141! Pat was legendary for his Triumph cams around here.
Cheers, John

 

[vibrac]

The area I am referring to is the wall of the intake port where it curves down to the valve seat. Number 5 in the picture. This is a automobile head and taller than a Vincent head, but the idea is to point the flow directly at the edge of the valve to increase flow at low openings.

John Mead

Ah! John No5 that is the place I was refering to now you have me searching for the recent reference that says dont carve it away .......

 

[johnmead]

I check one of the heads. It has @38mm intake ports. Also, the CP pistons are machined under the crown. Looks like I have the later topend. Now, the decision on running the MK4 or MK5 cams.

John Mead

 

[Monkeypants]

mk5 =more power and less strain on valve gear, easy decision. Listening to Mal Hewitt's salt flat racer waiting for the go ahead sold me on the idea. Big bumpy cams but a solid idle.
On changing port shape of the headsand the other changes, I would be worried that the Nascar man would turn it into a Nascar shape, good for going round in big circles at 7,000 rpm but no midrange or bottom, which is how the Nascar motors are. I think that you already have the good stuff on hand made by people who know Vincent hotrodding inside out, changing it might just mess that up.Hope you dont mind the opinionated posts, but as I learn more about all that has gone into these top ends, I have begun to realize they are really good items.
Glen

 

[johnmead]

The main concern with the TPV heads is that the exhaust port is too restricted. Besides the NASCAR guy, I got the same information from a Vincent Bonneville racer. The shape of the port to allow for a raised floor is good, however to use the stock exhaust Terry, et. all, created a restriction that will raise the head temperature at the exhaust port.

These heads were designed before Terry developed the MK4 & 5 cams so they did not take into consideration the increased flow these cams produce.

John Mead

 

[Monkeypants]

You might want to give Terry a call on the exhaust port question. When I ordered these top ends two years ago, he was waiting for flowbench results before making changes to the patterns. At that time he had both MK4 and MK 5 cams, though he wasn't selling the MK5s for road use until more testing (Mal Hewitt) had been done.
The MK4s have been around for years, so he would have taken them into consideration..
As John Mcdougall said when looking at the unusual seal arrangement on the TP valves" Terry never does anything without giving it a lot of thought first"

 

[davidd]

Carleton had the Terry Prince 500 head ported by a tuner recommended by Kevin Cameron. We have both used this guy for various items. He modified the heads extensively to make them flow. He modified the intake first. He then removed the "D" shaped exhaust port in order to get the flow up to a point where it balanced the intake. It added about 5 hp. But, I did not have him work on my heads and I have gotten within 1.5 hp of Carleton's engine.

David