MG Car Repair: MGB wiring, ballast resistor, wiring loom

Question
We have a 79 MGB that the engine died and we put in a '67 MGB engine in it.  The 79 is neg. ground the 67 was pos. ground.  I am going to replace the generator off the 67 with the alternator off the 79 because of the other wiring issues.  But the starters will not interchange.  Do I need to change out the starter?  There is only one post to connect wiring on that starter, but my wiring has connections for a post and two slip on connectors.  I'm not much of a mechanic but trying to learn on the fly.  Thanks.

Answer
Hi Arlan.  Yes, you can do this.  A 67 engine will fit a 79 vehicle, and you can use the 67 starter motor.  The change of polarity will not cause any problems, because starter motors are not polarity sensitive, they always spin the same way.  

Unfortunately, the 67 starter motor does not have a built-in solenoid, so you will have to fit a remote solenoid.   

There are two thin wires connected to your 79 starter with Lucar (slip-on) connectors.  One is the actuating wire (White with a Red stripe).  The second wire is White with a light Green stripe.  This is the bypass wire that goes directly to the coil, bypassing the ballast resistor which is built into your wiring loom.  When you buy the remote solenoid, make sure you specify one that has an extra connection built into it that is only live whilst the solenoid is activated.

The alternative is to fit the 12 volt coil from the 67 B and do away with the ballast resistor.