Thanks for the advice Bob. I am thinking of opening the plug gap to
around .052", and see how it runs. This would be the time for the GTech
meter, to see how the car performs on the road.
Jim, have you done any work on plug gap using your GTech meter?
Larry
Bob Palmer wrote:
>
> Larry,
>
> You will have to ask your dyno guy why he picked .048". Did he even try a
> run with your .063" gaps? In general, as you turn higher rpms, the energy
> per spark decreases. In a conventional coil and breaker setup, with the
> aforementioned gaps, the engine would probably start missing somewhere in
> the 5-6k rpm range (depending on compression and other factors. As we have
> discussed previously on the List, the purpose of the dual-point distributor
> is to increase the dwell and get as much energy into the coil per discharge
> as possible. .016" gap with a dual point is probably equivalent to about
> 0.08" gap or less with a single set of points. Of course, we all know that
> the MSD, in addition to providing multiple discharges at lower rpms,
> continues to give a single strong discharge at much higher rpms than even a
> dual point system would. However, even an MSD system has its limits and if
> the gap is too large, at some point the MSD will not generate enough voltage
> and/or current to produce an effective spark. Of course the other thing that
> can happen with a big gap is voltage breakdown, but this can happen at any
> rpm. So, is there really any advantage to a big spark gap? In my experience,
> I see a difference in terms of how smooth the idle is. I can't really say
> that I see any more power at the high rpm end so you should take the advice
> of an experienced dyno tuner on this count. I have been told by people who
> should know that a new set of plugs is worth a few more ponies on the dyno.
> Indexing the plugs is supposed to help too. BTW, based on the advice given
> on the List and elsewhere, I index the gap in the region between 3 o'clock
> and 6 o'clock. Again, without a dyno I can't confirm whether it really helps
> or not.
>
> Bob
>
> -----Original Message-----
> From: owner-tigers@autox.team.net [mailto:owner-tigers@autox.team.net]On
> Behalf Of Larry Paulick
> Sent: Friday, October 06, 2000 2:12 PM
> To: Bob Palmer
> Cc: Smit, Theo; 'Tigers'
> Subject: Re: Dist. Cap
>
> Bob, what are the advantages of gap, on both ends. I originally put
> .063" on my plugs, and the dyno man backed them to .048". This is with
> a MSD6AL, Mallory magnetic distr, 8mm Taylor wires, platinum plugs, big
> Mallory coil, and 9.5 compression ratio.
>
> Thanks
>
> Larry
>
> Bob Palmer wrote:
> >
> > Theo,
> >
> > The parameter that directly determines the spark voltage is the spark plug
> > gap. Back in the '70's the auto manufacturers went to very large gaps -
> > .070"-.090" - and consequently had to increase the cap size and make other
> > improvements in voltage standoff capacity. I'm not sure what gap is normal
> > these days, but bigger is better to a certain extent at least. I think you
> > will see that MSD recommends around 0.055" or so, depending on compression
> > ratio. For quite a while I ran an MSD with a standard Ford dual-point
> > distributor with 0.055" plug gap and never had a problem. This was with a
> > pretty high compression motor BTW. I think a good set of 7 mm wires will
> > work just fine too, in case you are after that "stock" look.
> >
> > Good luck,
> >
> > Bob
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