Ken...I went through this big time over the course
of about two years. The study I went through is where
that distributor chart came from. It's a bit lengthy
but you may want to take a read through of
http://www.teglerizer.com/mgstuff/a_stumble_at_cruise.htm
(watch for 'line wrap' of the above link... the list might
wrap the end to the next line)
This is the compilation of the email threads over
that two year period and what the result was
in fixing everything.
Paul Tegler
ptegler@cablespeed.com
www.teglerizer.com
----- Original Message -----
From: "Ken Waringa" <kwaringa@dynsys.com>
To: "ptegler@cablespeed" <ptegler@cablespeed.com>; "Dodd, Kelvin"
<doddk@mossmotors.com>; "MG" <mgs@autox.team.net>
Sent: Thursday, January 31, 2002 7:53 AM
Subject: RE: Distributor choices - marking locations
> Last night I had a chance to clean both vacuum advances looking for
numbers.
> The vacuum advance that came off the distributor with the 10 degree
> centrifugal advance had the following numbers: 10 15 5; 54425359. The
> advance from the distributor with 16 degree centrifugal advance had: 2 6
3;
> 54415328.
>
> Now. Looking at these numbers and studying Paul's advance chart it seems
> that the 10 degree dizzy has much more vacuum advance at lower engine
rpms.
> The 16 degree dizzy will have significantly less advance at idle and
relies
> more on the centrifugal advance than on the vacuum advance.
>
> Both vacuum advances are shot and will need to be replaced. Kelvin,
looking
> at the Moss catalog they only list one vacuum advance for each distributor
> type, but I have 2 different 25D4, 40987 distributors. Do you have a
> listing of the vacuum advance numbers that are available?
>
> And back to my original question, which distributor will be best for a
> stock, street driven early 1974 MGB engine with stock HIF carbs? Will it
> make any difference which one I use?
>
> Thanks,
>
> Ken
>
> -----Original Message-----
> From: owner-mgs@autox.team.net [mailto:owner-mgs@autox.team.net]On Behalf
Of
> Ken Waringa
> Sent: Tuesday, January 29, 2002 6:17 AM
> To: ptegler@cablespeed; Dodd, Kelvin; MG
> Subject: RE: Distributor choices - marking locations
>
> Thanks, I'll try to find the numbers tonight. They are very different in
> appearance. The one on the dizzy with the 16 degree advance looks like
the
> one pictured in the Moss catalog. The one on the dizzy with the 10
degrees
> of advance has the vacuum line connection to one side (not centered) of
the
> vacuum advance.
>
> Thanks,
>
> Ken
>
> -----Original Message-----
> From: ptegler@cablespeed [mailto:ptegler@cablespeed.com]
> Sent: Monday, January 28, 2002 4:43 PM
> To: Dodd, Kelvin; 'Ken Waringa'; MG
> Subject: Re: Distributor choices - marking locations
>
> ...and some are stamped around the neck of the
> vac unit right up at the nipple where the vac line
> attaches.
>
> Paul Tegler
> wizardz@toad.net
> www.teglerizer.com
>
> ----- Original Message -----
> From: "Dodd, Kelvin" <doddk@mossmotors.com>
> To: "'Ken Waringa'" <kwaringa@dynsys.com>; "Dodd, Kelvin"
> <doddk@mossmotors.com>; "MG" <mgs@autox.team.net>
> Sent: Monday, January 28, 2002 5:03 PM
> Subject: RE: Distributor choices
>
>
> > Ken:
> >
> > The numbers on the advance units are very hard to see. They are on
> > the face towards the distributor (if I remember correctly) and may need
> some
> > emery cloth cleaning to become visible. They are there.
> >
> >
> > Kelvin.
> >
> > > -----Original Message-----
> > > From: Ken Waringa [mailto:kwaringa@dynsys.com]
> > > Sent: Monday, January 28, 2002 9:00 AM
> > > To: Dodd, Kelvin; MG
> > > Subject: RE: Distributor choices
> > >
> > >
> > > Kelvin and all. I looked at the vacuum advances from both
> > > distributors, but
> > > could find no numbers or identification markings on them. I
> > > reconfirmed
> > > that both are 25D4 distributors, the only outside difference is one is
> > > marked 40897 A and the other is marked 40897 E. The internal
> > > centrifugal
> > > advances are different though. The one with the A is marked
> > > 10 degrees and
> > > the one with the E is marked 16 degrees. The mechanical stop for the
> > > centrifugal advance is clearly different as well.
> > >
> > > If anyone could advise which of these distributors would be
> > > best on a stock
> > > street car. I plan to use the HIF carbs on the car.
> > >
> > > Thanks,
> > >
> > > Ken
> > >
> > > -----Original Message-----
> > > From: Dodd, Kelvin [mailto:doddk@mossmotors.com]
> > > Sent: Wednesday, January 23, 2002 2:14 PM
> > > To: 'Ken Waringa'; MG
> > > Subject: RE: Distributor choices
> > >
> > > Ken:
> > >
> > > Someone out there please double check me, cos I've got a 5pm
> > > deadline and can't spend any more time on this.
> > >
> > > The records I have show the 40897 dizzy as being
> > > original fitment on
> > > 62-67 MGB definitely not for the 74 cars you have. Lucas
> > > shows a 41288 unit
> > > as the superceded replacement. The first 5 digits give the
> > > part number, the
> > > suffix is not used for identification.
> > >
> > > Any unit with the same 5 digits should be identical, given the
> > > vagaries of production line, later modification and divine
> > > intervention.
> > >
> > >
> > > Based on dubious years of swapping bits, I'm banking
> > > that both your
> > > engines got dizzy swaps from the original rare bird 41491 to
> > > the much more
> > > available earlier unit.
> > >
> > > If you get me the part numbers off the vacuum advance
> > > units which
> > > may be 54411230 with the following legend 5.13.10 underneath
> > > I can be of
> > > more use.
> > >
> > > The problem is what carbies are you using? HIFies, or HS?
> > >
> > > It sounds like you may have a common case of mix and match,
> > > and you are
> > > asking the right questions to figure out what combination
> > > will work the
> > > best. First we gotta figger what you really have.
> > >
> > >
> > > all the best
> > >
> > > Kelvin.
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