E: Engine Valve Springs

[davidd]

I have been on hold with the project for several years. I have tried to get it going again, but I have not been able to find the time.

I am at the point that I have to have valves made. Unfortunately, there are enough small mods to the valve that it means making a new one. I am reasonably certain that G&S will knock them out, but I have to settle on a final valve design. This means prototyping a valve, which really needs to be done by me. That is the hold up.

Above is a stock valve and the spring height is not tall enough to reach the proper installed height.

For racing there is a huge difference in two springs, beehive on left and stock on right.

One of the changes is a different lock system to rid the system of the circlip, which has been a weak link in the system.

If you are just running on the street I would consider Mike Hawthorne's beehive conversion.

The photo shows a stock Vincent retainer and locks. It looks like Mike makes the retainer from steel. He mentions the other GS locks being available.

These springs are quite inexpensive because they make thousands of them for the Ford 32 valve 4.6 litre high performance engine. I paid $12 for mine. The titanium retainer is more at $15. Ultimately, the problem I have is that the stock valve has trouble with lifts approaching 0.500". The button on the valve shoulder hits the top of the valve guide. This means making a valve with a higher shoulder. Greg Brillus had to do this on his twin racer. The spring will definitely move 0.500", but the valve is not really designed to do 0.500".

David

 

[timetraveller]

I had some special valves made with the thicker part of the stem 0.1" longer than standard. That took care of the extra lift. However, I struggled to find a suitable beehive valve spring and when I eventually found some, although the catalogue gave a maximum lift of 0.5" there was a note with them stating not to use more than 0.45". The valve spring retainers are different to the Vincent circlip ones and Roy Robertson very kindly machined new grooves in the upper valve stems to take the new retainers, which are more like Gold Star ones. I lent the parts to Mike Hawthorne to copy, and gave him the details of the supplier, but he has had some problems with his engine and, I think, valve bounce.

 

[Monkeypants]

When Terry Prince and Fritz Egli Jr used the Mercedes Formula 1 Cam development program loaded with Vincent data, it showed no power advantage in lifting beyond .440" at the valve. This was a bit of a shocker to Terry as he was always a believer in getting the highest lift possible. The program indicated a lower rpm for valve float at .5" than at .440", which is logical. In any case, it gave .440" with radiused followers as the maximum ideal lift for performance in a Vincent engine. Those are big valves that Irving plunked in there!
Of course using a higher lift like .5" would also shorten valve train life greatly. .440" might be trouble enough in this regard, time will tell. With the curved followers everything looked happy at 1500 miles, cam and follower surfaces just starting to polish up.
The max HP rpm figure given for the .440 lift cam was 6500, which is about 1000 past where one can safely go with standard type crank and cases. So even to fully utilize that much cam one needs to think about a Picador type crank and some better cases.
I believe Mike Hawthorne's Flash engine broke up into many pieces recently, not sure what his crank type is, or what the cause was. I can guess that very high rpm was involved!

Glen

 

[Marcus Bowden]

Yes, Speed is Expensive. and time-wasting before one gets there. Max Lambky is a prime example, believe Mike Hawthorne is going to be his new pilot and a lot of "T" shirts have been printed.!!

 

[davidd]

Renwick provided the cams for my engines and they had lift up in the .490" area. Max power at 6900 rpm. Power numbers for the single were 43 BHP. None of the lower lift cams provided this power. Max power for the Mk2 is about 37 BHP at 5900 rpm.

For landspeed I have reved to 8500 with no float, but there is no power up that high. It is also 5020 ft/min piston speed which is very high.

I don't know what to say about the .440 lift max. It could be true. I have found the Vincent to be very reliable, which could mean that the power is still too low. I have never encountered any inclination of the valves to float or detonation.

I have run stock valves with the high lift cams, but it does not work 100%. The last engine I built the button hit the intake valve guide even though all the components had worked before. Some clearance went away during the rebuild which was so small it could not be felt by hand. I took this to mean that I was right on the edge of usability. My hope was that if I moved the shoulder of the valve up a bit I could get back to setting up the system nearer to the middle, rather than the edge.

As for Mike, it is difficult to know about valve bounce without knowing the installed height and pounds generated on the seat. I do know these springs work on the Fords and there is a Gold Star in AHRMA that has been racing with these spring for years. I don't think the beehive springs will give more power. For me it was a path to getting a better valve design for racing (to help the clearance issue) and spring set-up that was light and simple.

As for the blow up, I suspect it was just like my blow up. The big end bearings crunched up and the stroke became considerably longer, the piston hammering the head until something gave. It is a 600 also.

David

 

[Robert Watson]

So far I am no further ahead, probably because I wasn't clear at the outset.

Where can I get decent valve springs for a street motor today that will just pop in without reinventing the whole valve train??

 

[passenger0_0]

Robert, the last three motors I did all had clearance between inner and outer coils and operated fine. Provided you have around 70 lbs seated pressure you will not have any issues with a stock motor. I personally wouldn't bother moving away from stock components for a standard bike.

 

[Robert Watson]

I was told by John McD who built MANY motors that around 100 seat pressure and 150 over the tops.

The originals do have not unreasonable seat pressure but are below 2 in free height which Richardson says should be replaced.

 

[davidd]

I too have had a few unknown origin springs go soft. I prefer to replace them every season. The beehives are generally run with slightly lower pressures. 90 Lbs. on the seat for the PAC 1223 spring that we have been talking about here.

David

 

[Monkeypants]

Terry did have the full RD setup on hand, but he is winding that parts business down.
I recall some info from my 2004 John McDougall top end redo and switch to RD springs.
At that time RD had a minimum batch size of something like 50 engines and John did not want to commit to that. He and Dan had split an order years earlier but in 2004 John had used his allotment up.
So I ordered a set of RD springs with all the special bits from Terry Prince. Years earlier he followed John's lead on the RD springs. So as mentioned this am, Terry may still have some. I believe he still does the top end kits, which also utilize the RD springs and special components.

Another quality name in valve springs is Kibblewhite, not sure if they offer Vincent valve springs.

Glen