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Alternator wiring

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I have a 510 that I'm makinging a new harness for and it's in the middle of becoming a track car and it has a alternator from a 620 how do I wire it thanks

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For internally regulated.



For externally regulated, it's identical, but the VR plugs into the back, like this:



The positive output of the alt always goes to Batt+ via a large wire, which can be routed via the post on the starter solenoid. Put an inline fuse or fusible link on this line. (Shown as "A" above.)

The ground connection always goes to a good ground. Match this gauge wire to the positive output. (Shown as "E" above.)

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Well if a 510 it would normally have an external regulator so if the 620 alternator is from a '73-'77 truck then it is an external one and will just plug in.


If you are making your own harness you could start by having it already 'converted' to take an internal regulated alternator from a '78 and up Datsun/Nissan ... anything.

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Or just use a 1-wire alternator...




But, on an all out race car, I still use an internal, but then I use a full throttle switch to cut the field coils,

so that under full throttle, the drag from the alternator goes almost to zero. (belt & bearing drag still there)


On a little 4-cylinder, 6-8 hp means a lot.

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A one wire alternator only uses the charge light to "bootstrap" the alternator into charging.  Once it starts charging, disconnecting the light does not make the alternator quit charging, until the engine is shut off again.

You need an external regulated alternator, and disconnect the field wire to the alternator between the regulator and alternator to remove charging drag from the alternator.

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Alternators vary in efficiency but the lower range seems to hover just over 50%. So 2 HP will make one HP of alternator power. One HP is 746 watts.  Now unless you are drag racing with your lights on high beams, heater on high and the wiper on and the battery was dead you are only drawing about 20 amps or less for the ignition system and gauges. So to make 20 amps @14 volts (or 280 watts or about 0.4 HP)  you will need about 0.8 HP from the engine, or say 1 HP for good measure.  (I think the EI system draws about 12 amps)


If the alternator is capable of 80 amps it takes 3 HP to make. 80 X14= 1,120 watts X  2 (50% efficiency) = 2,240 watts of work from the engine / 746= 3.007 HP

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