>From Randy:
>>>>>>>>>>>
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)
>>>>>>>>>>>
Just to add some personal experience to Randy's comments above: I have performed
a similar modification to my '79 Esprit that has been well documented in the
Lotus ReMarque newsletter (Charlie Seabrook article). In a nutshell, there is
a lot to be desired in the performance of a US emissions dist, when compared to
its European equivalent that doesn't have to pass an EPA dyno test. The US
dist. had a 10 deg vaccum retard (to 0 deg at idle), when you get above idle
it catches back up to 10 deg BTDC (static Euro timing), but then you do not
reach full advance (about 30-35 deg BTDC) until over 5500 rpm because of these
humongous advance springs. Following the article I brazed the plate (so no more
vaccum advance) and replaced the springs with weaker ones from a "Cal Custom"
kit for a GM 6 cly. You also limit the amount of advance by changing the
bushing that serves as a limit pin. Net result: you idle at 10 deg BTDC and
get full mech adv to 35 deg BTDC by 2500 rpm (just like the Euro distributor).
My economy has not suffered from what I can see and the performance difference
is amazing! I can only conclude that the US distibutor was a kludge to pass
emissions in the cheapest manner (my car did not come with a cat conv). The
Euro dist is the way the car was designed to run. With the US advance springs
it was like having turbo-lag as the advance was slowly rationed out till 5500
rpm was reached. My distributor is Lucas (45D4?) w/luminition. This makes for
a nice setup: optical chopper wheel with no more vaccum advance wobble and
mechanical rev limiter.
-Bob T.
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