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Re: [Mgs] Pertronix Flame Thrower distributor

To: mgs@autox.team.net, Henri Lefebvre <71mgbgt@gmail.com>
Subject: Re: [Mgs] Pertronix Flame Thrower distributor
From: Rick Lindsay <rolindsay@yahoo.com>
Date: Wed, 10 Jun 2009 09:00:59 -0700 (PDT)
Morning Henri,

You'll probably get lots of opinions regarding this change.  Paul Hunt always
offers good advice.  I'd certainly lean toward his advice.

Maximum advance needed has to do with the burn rate of the charge - and that
changes with engine speed and compression ratio.  If I remember correctly,
higher pressure charges burn more slowly - so you need more advance for a high
compression engine.  (Someone please check me on this.  Its been a while.)  If
it were mine, I would look up the advance curves and set the new unit to match
the factory specs.  This guy has done a TON of research in this area:
http://www.teglerizer.com/

As for the vacuum advance, I always prefer the ported advance (on the carb)
where the throttle disk covers the vacuum port in the choke until the throttle
is opened.  I find that it offers a smoother idle.  Remember, the original
purpose for the vacuum advance was to modulate the timing to compensate for
engine load.  The centrifugal advance is the base correction for engine speed.
The later model cars tweaked with the advance to try to control emissions.
Some cars even used timing-retard units in the pursuit of passing emissions
tests.  I view these efforts as signs of a dieing era.

Personally, I tune for performance and driveability.  We use our cars a tiny
fraction of road-time of the tens-of-millions of Hondas.  I don't think a
finely tuned little MGB is going to melt much polar ice.  YMMV ;-)

Regards,

Rick

--- On Wed, 6/10/09, Henri Lefebvre <71mgbgt@gmail.com> wrote:

> From: Henri Lefebvre <71mgbgt@gmail.com>
> Subject: [Mgs] Pertronix Flame Thrower distributor
> To: mgs@autox.team.net
> Date: Wednesday, June 10, 2009, 10:38 AM
> I recently installed a Pertronix
> Flame Thrower distributor in my 71 MGB GT.
>
>  
http://www.mossmotors.com/SiteGraphics/Pages/flamethrower/flamethrower.html
>
> For proper ignition timing purposes, would anyone be abIe
> to provide
> the following information:
>
> 1 - Distributor mechanical advance of this
> distributor:    10 degrees?
> or 20 degrees? or other?
>
> 2 - Vacuum advance:    connection to manifold? or
> carburettor?
>
> 3 - Recommended Ignition Timing, based on the above and
> engine year?
>
> All and any information and recommendations welcomed.
>
> Thank you,
>
> Henri
> 1971 MGB GT
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