Marcus,
Ooops, I don't have a good copy of your address, and today all the Brit-car
mail came in with MJB as the sender/author/return/etc. Ah well...
I do believe what your mechanic was talking about is to just disable the
vacuum advance portion of the distributor. You want to leave the centrifugal
part alone. A street engine with the timing locked at like 37 degrees would
be hell to get started, and ping like you wouldn't believe at low revs.
To do this, you set that movable breaker plate to it's normal position,
such that the phasing is right, prop it up square, then weld or braze the
two pieces together. After doing this, the vacuum advance will no longer
work (or even be there), but the centrifugal still will do it's job.
The centrifugal advance's job is to change the timing in direct relation
to the revs. This is by far the most important part, and the only part used
in many high performance designs (as your mechanic was saying)
The vacuum advance is to modify the timing set the centrifugal according
to engine load. The reason is to get improved fuel economy at partial/light
loads. Later cars, especially Triumphs, also used the vacuum to trim out the
timing for emissions reasons.
Needless to say, I would not recommend messing with it unless you know
what you want, why you want it, and how you're going to get it. New breaker
plates (the only problem you're curing with this) are not *that* expensive...
Randy
randy@taylor.wyvern.com
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