Paul :
The problem is one of resonance. At certain engine speeds, a single
spring gets to bouncing until it doesn't work very well. The second
spring, which is much lighter and has a very different resonance point,
was Triumph's attempt to solve the problem. Some TR3s even used a third
spring !
On many modern engines, the inner spring rubs against the outer spring,
to add a little friction and damp the vibrations (kinda like early
friction shock absorbers for suspension springs). BFE sells a set of
these for the tractor engine, probably has them for the 6-cyl, too.
Randall
59 TR3A daily driver - with BFE valve springs
Paul Mitchell wrote:
>
> The title says it all: one spring brings it closed when it's open , and
> the other, er, brings it closed when it's open. Why two?
>
> Paul
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