Dual Distributor Points Wiring for 620!!!

[Benkrwn]

I've recently got my 72' Datsun 620 on the road and have been battling and working all the bugs out of it. But there's one that really boggles my mind?? The disturbutor is a stock dual point set up. My questions is "Are each set of points Indepently wired or does one wire power both?" There are two leads coming out of my disturbutor. One is cut off!! WTF?? Does anyone have any idea where these leads go??

[datzenmike]

Power comes from the ignition switch to the coil and through it to both sets of points which close and conduct to ground allowing current to flow through the coil, effectively 'charging it up', and then opening. The current flow stops and causing a high voltage discharge. One set of points closes and begins charging the coil. The second set close, but this does nothing as the first set are already conducting current through the coil. In time the first set open but this does nothing as the second set as still closed. Finally the second set opens and breaks the circuit and the coil discharges.

 

Now by disconnecting the second set of points the first set will open and fire the coil about 4 degrees sooner making them the advanced set. By connecting the second set of points the ignition fires later making them the retard set.

 

Ignition timing with proper advance is set on the first set of points, thus, depending on several switches and temp sensors and relays, the second retard set can be applied to the timing to reduce emissions under certain conditions.

 

I would disconnect the retard set and just run one. Set the timing and forget about all the wiring, relays, sensor and switches.

[Benkrwn]

Thanks for reply. If I wanted to use the second how would i wire them in? Or make them work?

[datzenmike]

There's no advantage to this. It's totally an emissions thing... oh I see. Good old Kalifornia. Check your regulations. A '72 is emission exempt but you may have to have all emission parts on the vehicle for a visual pass. I'm not knowing.

 

 

Of the two distributor wires, the Black one goes directly to the coil - side. The Blue/Yellow goes to the Distributor relay. The distributor relay selects which set of points are used with input from a temp sensor in the cab, a 4th gear tranny switch and a carburetor switch. Likely one of these has failed and the P/O disconnected the retard set so it would run properly.

[DanielC]

The second set of points was there for engine emission control. They was put in the circuit by a relay that was engaged, when certain conditions were met.

On a 1971 521, the second set was used only in third gear, part throttle. The points were set 5 distributer degrees retarded from the primary set, and that ended up being 10 crankshaft degrees.

Since the points were put into the circuit by a relay, energizing the points relay by a switch would cause the second set of points to become active.

A manually operated anti knock switch?

[Benkrwn]

Thanks again!! I'm going look for the failed switch and replace it!

 

 

[datzenmike]

I would get a factory service manual if you are serious about setting the emissions system in order. Or any thing else on your Datsun. There's invaluable info there.