The Knowledge - Velocette Owners Club

#3793 Closer exam (with a magnifying glass) shows tiny but undoubtful marking on the ex valve. What
surprises me is how small it is, versus inlet valve badly damaged. Inlet is marked M2/7, ex. M2/17N80.
Could Nimonic valve be so much harder than inlet material? So, or the springs are too weak, or the
chronometric tacho pessimistic and I over revved, or both.
#3801 All you ever want to know about valves can be found here
www.gsvalves.co.uk/technical_information.htm (download the pdf). G&S have manufactured valves
since the 40's, they manufacture valves for the VOC, Grove et al. The guys there are really helpful, and
rather than telling me to "go away" when I stretched and tuliped a valve that may not even be of their
manufacture, they were really interested and wanted to help. Regarding Aluminium valve caps, most of
the UK Velo racers use Nick Payton valve caps and springs and as yet I know of no one who has had a
failure. PS Nick springs are of Porsche origin. You need to set the installed lengths to 1.310 exhaust,
1.340 inlet. On a Venom or Viper this will probably require machining a counter bore in the head and
lining it with a shim to set the length and avoid hammering the Ali.
#3784 Just a small point re rotating valves. Veloce designed the collar arrangement to allow the valves
to rotate and thus even out wear etc. It is possible that the inlet valve can be struck by the exhaust
valve with some enthusiastic over-revving. If the springs are tired this happens more easily. Also, is the
valve timing correct?
#3787 Well, Velocette may have said that the design would allow the valves to rotate, but that doesn't
mean that the valves actually did. A careful examination of the striking points on the ends of my
extensive collection of used valves shows line contact from the rocker on most of them. And the ones
that do show wear all around on the striking point would do so after removal (to reseat) and
reinstallation. While it's true that the valve and collar assembly is not prevented from rotating, the only
way that they could rotate is if the spring pressure was released during operation, like during valve
float, eh? Even then, they would have to have something to cause them to start twirling in the guide,
wouldn't they? And what would that be? No, it looks like a propitious sales gimmick to me. " By golly,
the way those collars are designed would allow rotation, no? Well let's advertise it as a benefit, then"
#3794 Do you have / can you share any more details on HOW to make a coil spring conversion or point
me / us towards a source.
#3795 The easiest way is to contact Nick Payton on 0208 540 2118 and ask him.
#3884 I copied a Webco (US) alu alloy coil spring conversion in titanium, using B50 BSA (Goldstar)
springs. The Webco conversion of top and bottom spring seats retained by the Velo split collets were
known to fail due to the shallow wedge angle of the Velo collets pulling through the soft alloy collars.
Absent a Webco kit to copy in titanium, you'll have to get a set of the springs that you want to use and
define the configuration of the necessary collars, turn them up and install. Or buy a set that I'm told that
Nick Payton offers in England. The critical points are that the springs are compressed to within
.060"-.100" of coilbind at full lift (max. Tighter will lead to failure) and the seat pressure should be in the
area of 80-100#, with 220-240# at full lift. You can check these numbers on a bathroom scale under a
pillar drill. After making the titanium spring seats (collars), shim under the bottom one to get the
installed height correct and use a phenolic insulating washer under the exhaust spring seat in order to
prevent heat damage to the spring.
L #3897 Members may know from previous requests for help that I am putting a MKII KSS engine
in a Viper spring frame. I have to make a new head steady for the KSS in the spring frame as the frame
lug is further back. The old steady of tube with flattened ends has one hole elongated. Was that to
allow for variability in manufacture or for the engine to move?
#3899 Make your head steady to fit with round holes. The idea is to hold the top end still, not let it
shake about. I have a KSS / RS hybrid and I love it.
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