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MG MGB Technical - positive or negative

I have a engine from a parts car and I want to try to start it. I need to know witch wire to connect to the coil ( positive or negative ) and witch side of the coil I connect the wire to.
GK George

If the engine is out of the car, use a standard 12V coil. Connect a separate battery, positive terminal to coil terminal marked positive, connect coil negative to points lead on distributor and battery negative to engine cylinder block. Feed starter with positive from battery
jim soutar

The type of starter motor that you have will be a big help in determining which polarity that you have. If there is a single, large wire going to the starter you have a positive ground engine, unless someone has converted the ignition to negative ground. If you have a starter with a solenoid mounted to the bottom of it, you have a negative ground system. Proceed as Jim has outlined. RAY
rjm RAY

Thanks for the responce. The engine is out of the car and I want to try to start it before I put it in a car. I am a collector of MGA's and the starter is the same with no solenoid on it. The car must be positive grond.
GK George

Since converting a positive to a negative ground really only involves the generating system, I would not think it would matter on the starter motor. or the engine.
Bruce Cunha

I think you are right bruce, just be consistent between the coil and starter.
Stan Best

The starter doesn't care what polarity is fed to it. The coil will be more efficient if connected with the terminal marked + to the positive potential of the set up (+ to ignition voltage for a negative ground vehicle, to ground for a positive ground vehicle). When I say more efficient, I mean that the spark will be a slight bit higher if it is connected properly, but not sufficient to be noticed unless the whole engine is operating very poorly. Cheers - Dave
David DuBois

This thread was discussed between 23/04/2011 and 26/04/2011

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