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Re: Speedo calibration bust!!! OFF LIST

To: larryhoy@prodigy.net, "Mgs@autox.team.net" <Mgs@autox.team.net>
Subject: Re: Speedo calibration bust!!! OFF LIST
From: James Schulte <schultejim@prodigy.net>
Date: Sat, 25 May 2002 22:14:50 -0700
Larry,
I've pulled several engines w/o tranny but only one w/tranny.  It's not that
big a problem with me.  I teach and coach swimming all winter but have July
off.  So I have time to do it.
I wanted to detail the engine bay anyway if the car doesn't get sold soon.
It is such a fun car and rides very smooth compared to the 70B we have.  I
hate to get rid of it, but I want a CGT to travel to the far events like
Vermont this Fall.
Jim

Larry Hoy wrote:

> James I wasn't ready to tell you this yet cause I don't have all the
> answers but if you are willing to pull the tranny the interal
> distributor drive gear can be changed to the later gear and this will
> solve the issue.
>
> There are no 1280 speedos that fit the larger holes in your dash.
>
> Larry Hoy
>
> >
> > Listers,
> > Anyone out there want to swap an excellent 1973 model O/D for
> > a late model O/D so I can get my speedo to read correctly on
> > my 78B ? Jim in Harleysville, PA (34 miles NW of Philly)
> >
> > Larry Hoy wrote:
> >
> > > James, I think you're in trouble.  I now think that there are no
> > > 1280tpm speedos that are the 4" size.  Turns out that the
> > first chart
> > > on Skye's site is missleading and the 1280 speedo listed as 1967 is
> > > really for a 1968 model car which is the smaller 80mm size.
> > >
> > > What all BMC manufactures did in 1976 was change to a standard 1000
> > > tpm speedo and made the gears in the transmission work for
> > the speedo.
> > > Prior to that the speedos were unique tpm for each car.
> > (For instance
> > > your gauges are the same gauges found in the Triumph Spitfire).
> > >
> > > You may need to resort to some 'extremes'.
> > >
> > > 1) An electronic speedo from VDO
> > >
> > > 2) A transmission from a speedo shop
> > >
> > > 3) A new face plate for your present speedo (I thought that
> > Nissonger
> > > did this)
> > >
> > > When I put in my V8 in the car I had to do the #1 option,
> > since I have
> > > a Chevy 5 speed transmsission.  I've attached images of the
> > small VDO
> > > speedo gauge.  The biggest 'give-a-way' is the red tip on
> > the needle,
> > > and the digital odometer.  I used the stock MG facia ring.
> > >
> > > Larry Hoy
> > >
> > >
> > > > Subject: Re: Speedo calibration bust!!! OFF LIST
> > > >
> > > >
> > > > Larry,
> > > > Thanks for the info.  I'll wait for your final analysis. Jim
> > > >
> > > > Larry Hoy wrote:
> > > >
> > > > > > That's a different size speedo... it wouldn't fit in
> > your dash.
> > > > >
> > > > > Max, Jim, Bill,
> > > > >
> > > > > I could be wrong but I think the 1963-1967 and the
> > > > 1977-1980 cars are
> > > > > the 4"(100mm) instruments.  The 1968-76 cars are the 3
> > 1/8" (80mm)
> > > > > instruments.
> > > > >
> > > > > His OD transmission is from a 1973 car that was
> > originally matched
> > > > > with a 1280 tpm 80mm speedo.  His car was originally
> > built with a
> > > > > 100mm 1000tpm speedo.  According to Skye's web site the
> > > > 1967 cars were
> > > > > equipped with a 1280tpm 100mm speedo.  Soooo the 1967 1280tpm
> > > > > 100mm ought to fit in his dash and solve the problem.
> > > > >
> > > > > Consider that his car goes 60mph and registers 80mph a
> > > > ratio of 1.33
> > > > > (80/60).  The speedo ratio would be 1280/1000 which is 1.28;
> > > > > almost identical.  After the change the 60mph car
> > should register
> > > > > around 62mph. I bet if Jim REALLY knew how fast he is going when
> > > > his present
> > > > > speedo is registering 80 mph he'd find he is going 62.5 mph
> > > > which is
> > > > > what the 1280 tpm speedo would register.
> > > > >
> > > > > There is the one 'gotcha', I'm not convinced that Skye's charts
> > > > > are accurate.  In fact he has two charts on his site
> > that seem to
> > > > > be in conflict. (By the way this is why I've copied Bill Dudley
> > > > > with this message, his 1967 MGB is a one owner car.
> > Bill, would
> > > > > you
> > > > check your
> > > > > speedo and see if it is a 1280 tpm 4" speedo?).  I suppose
> > > > that will
> > > > > be sorted out when we here from Bill, who I think is out of
> > > > town right
> > > > > now.
> > > > >
> > > > > Max the 21 vs. 22 tooth gears wouldn't be able to make enough
> > > > > difference to even justify the change.  The gear INSIDE the
> > > > > transmission that drives the pinion changed over the
> > years, that
> > > > > is another solution. However it requires the removal of the
> > > > > engine, transmission, and then the swapping of the
> > internal speedo
> > > > drive gear.
> > > > >
> > > > > On other solution. Any COMPETENT speedometer shop can make a
> > > > > transmission to change the ratio.
> > > > >
> > > > > OK now one last suggestion, then I'll quit.  VDO makes a 4"
> > > > gauge that
> > > > > is programmable.
> > > > >
> > > > > Larry Hoy

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