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MG MGB GT V8 Factory Originals Technical - SD1 speedo and rev counter types

Hello


Can I use the automatic gearbox SD1 V8 speedo and tach for my manual conversion dials?

I assume the tach would be OK as it works on pulses, but do the two types of gearbox have the same drive for the speedo?

Thanks, Liam
Liam H

Hi Liam,

the internals of the early SDI tach are interchargable with the internals of the B 1800 instuments of this period. Tey are also scaled up to 7K rpm. In my car it works since 1981. Just a simple drop in swap with changing the dial and the pointer. Do not forget to mark the relative position of the pointer with a pencil inside the instrument before taking it apart! If yo can locate the scale of a BGTV8 factory tach, the P6B internals would also work fine as they were also scaled up to 6K rpm.

With the speedo, i am not so sure. I have one from a MGC installed and it came with the 3.3 axle and works acurate enough with the LT 77 gearbox and drive from the 4 od box. The readings are +/- 5% to those from a Garmin GPS.

Nowadays i would not spend that much money and time into a speedo as the cheapest electronical bicicle speedos are more precise than any other instrument aboard the MGV8 and can be used for speed limit controll and monitoring trip and over all milage and there are multi function clocks integrated in these funny little things too, although they are not allowed to be used during rallys here.

Hope this helps

Ralph



Ralph

Liam, the tacho will work fine & the rev range will be correct because it's the same engine. The speedo accuracy depends on the diff ratio & the size of the rear wheel/tyre combo. You'll have to reduce the diam. of the SD1 dials by about 1/8" to fit into the MG cases. That's easy enough as they're made of perspex. You'll also have to drill small holes in the dial faces to accomodate the Ign. & Hi beam lights unless you use external ones from a later model. The trip reset comes thru the lens of the speedo, so a new lens will be needed. The original SD1 one is curved & won't fit very well. This is the approach I used & the only down side is ,the illumination is not the best. It is readable at night but it is on the dim side.
If you're using the Rover gearbox, the speedo cable from the auto should fit OK. HTHs Barrie E
Barrie Egerton

This thread was discussed between 13/06/2007 and 14/06/2007

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