[TR] cam idle update

[Brian Jones]

Even though the engine gets faster under acceleration, it is still burning
fuel that insists on burning at a constant rate. To get the maximum bang for
the buck, ignition must occur earlier and earlier in the cylinder's cycle
the faster the engine runs, so that the energy from combustion can
efficiently move the piston on it's down stroke. Without this advance,
ignition would occur too late to occur at the piston's optimal point for
combustion.
Advancing the spark in this way occurs through two mechanisms: vacuum and
mechanical. Vacuum is created as the engine runs. More acceleration = more
vacuum. The mechanical advance mechanism is in the distributor - weights
held by springs spin further away from the central shaft the faster the
distributor shaft rotates. This deflection moves to further advance the
spark.

The 'curve' is a chart showing how much deflection there is in a particular
mechanism for a given rev speed. Imagine plotting engine revs on the x-axis
and degrees of deflection on the y-axis: You'd get a curve. Change the
weights, or change the springs - or both - and you'd get a different curve.

If the supplier of your cam didn't specify a recurve of your distributor,
chances are you need not play with it. Just make sure it is working well.
Also, I'd recommend making sure to get right what you have now before you go
and change another dimension to the car. Madness lies ahead, otherwise...

Is your valve lash correct for your cam?
Is your timing right for your cam?
Is the dizzy fully operational (points good, good gap, HT, rotor and cap OK
etc.)
Do you have a good spark
Is fuel delivered OK
Are the carbs set up OK?
Is the coil OK?

Good luck,

Brian


On Tue, Aug 18, 2009 at 7:20 PM, Gary Nafziger <nafzigerg at yahoo.com> wrote:

> thanks everyone for responses.  I always feel better after getting feedback
> with any problem I bring to this place.  I loved the link someone sent that
> included exhaust sound from the S2 cam.  Also thanks tony for the links to
> tr-6 tuning information.  very helpful.
>
> I just got back from another run in
> the car and the problem is getting worse.LOL  It's now missing more at
> highway
> speed which it never did before.  Actually thats good news!  I feel its
> more
> fixable than thinking about changing cam timing or even going back to stock
> cam.
>
> With all new spark plug wires, coil, dizzy cap, rotor, points
> .................i never did anything to the dizzy.  It's cleaned up but
> stock.  I don't understand "curving" a dizzy.  How does curving a dizzy
> help?
> what does it do? and will that help idle?
>
> thanks again!
>
> gary n.
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