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MG MGB GT V8 Factory Originals Technical - Tachometer

Hi Guys,

I've just become the happiest guy in the world. No, my wife didn't have a baby (we're both in our 50's). No, I just bought an MGB V8 roadster. Stock Olds 215, stock MGB overdrive & stock rear. My first project is to try to recalibrate the stock MGB tach so that it doesn't read double. I'm planning to solder in a 100k ohm pot into the circuit board, as outlined on Zak's home page, but I have one question. The pot has three leads, one on each end and one in the middle. Which two do I use to solder into the circuit board?

Thanks for your help. Allan
Allan

You solder the middle one and either one of the ends it doesn’t matter. It’s designed so that it can be used to increase one circuit as it lowers the other with the same adjustment for applications that require it, but only one side is required for our purpose. I had to e-mail Zak for this information myself.
George Champion

Find the two legs that when you put a resistance meter across them an turn the pot, there is no change in resistance.

Take one of the leads that creates the no change in resistance and the odd lead, and you now have the lead to the wiper and one to the resistance track inside the trim pot. Connect these two leads per Zak's website, calibrate to the known speed and you are done.
Phil

This thread was discussed between 21/05/2002 and 22/05/2002

MG MGB GT V8 Factory Originals Technical index

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