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Just bought a 521


mainer311

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60A, not 90A. Extra juice to run 55/65W H4’s all at the same time. I’d rather have a healthy margin than be slightly negative on the ammeter. High beams will be sucking down almost 20A by themselves. That doesn’t leave much for everything else on the stock alt.

 

In this case, I killed two birds, since the stock alternator sounded like a box of rocks. After I pulled it out, I gave it a spin and it was on its way out.

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looke like they put inserts in the holes for the smaller thickness L16 bolts.

 

60ampes should be enough. run H4s and Hella 500 bumber lights) above idle is fine w/o the wipers and heater on.

 

 

when My bolts were breaking ai was running a 510 alternator mount on the block. This was breaking my bolts and one is stuck in there and had to use shorter. I went back to the stamped mount.  I also run a turn buckle type alt tensioner as I hate the stock slider bar used as they alwasys semm to loosen up on me. or the bracket breaks cause of vibration or leeting the bolts run loose.

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I dont understand the big red wire from the + out of the alternator. where the stock white red stripe wire?

 

I'm not running that dinky white wire with a 60A alternator! I upgraded the output wire to a 6AWG red ultraflex wire. The smaller white wire from the VR is bolted to the starter post. The ground is a matching 6AWG to the block.

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Can anyone elaborate on the dual points setup? I read about it in the Chiltons manual and it’s clear as mud. As far as I can tell, the retard set of points are only activated under a certain set of conditions, while the advance set of points is just always running. The phase difference between the two is something like 5 degrees, so when the retard points are activated, the opening and closing overlaps by 5 degrees, and when they’re not activated, the truck just runs on whatever timing the advanced set is at. Does that sound right? Is there anything I can do to simplify this? Can I remove the retard set?

 

Also, why can’t the Pertronix unit be used in the dual-points dizzy? Does it not fit where the points mount? Or is the fitment much more complicated for some other reason?

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Not to sure about the 2 sets of points... I think i has to do with coil saturation.. ive heard some remove the second set and only run the primary.... but not sure...

 

And petronix only fits a single points dizzy... Dp tried to put the one i send him on a dual and nothing lined up... I think there is even a diameter thats different..

 

I think you can get a complete electric dizzy from the 620 ... not sure what else might be needed...

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You are close on the function of the second set of points.  They are retarded 5 distributor degrees.  That means they open later that the primary set of points.  I know you know that, I am not trying to be condescending.

 

The second set of is connected in parallel with the primary set of points, by a relay.   That relay is controlled by several switches on the carb, transmission, gas pedal, and clutch pedal.  Basically, the timing is retarded only in third gear, part throttle if the clutch pedal is fully out.

 

When all the conditions are met that activates the secondary points relay, since the points are then wired parallel, the coil does not fire when the primary points are opened, because the secondary points are still closed for 10 more crankshaft degrees.

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Was that all for emission control? Why retard timing under a very specific set of conditions?

 

Also, is there an easy way to tell which set is advanced and which is retarded? The wiring schematic from the forum isn't clear. As seen below, it shows R and A, but only the advanced points show the black/yellow wire going anywhere.

 

9luxgwo.jpg

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yeah from what I was told it was for emissions.

 

Take the dizzy cap off and turn the motor you should see one set of points opening, that is the primary.  Secondary won't even open because you aren't meeting the necessary conditions that DanielC talked about.  At least that is what I saw when I swapped my dual points for a pertronix (only one set opening/closing).  And like crash said pertronix won't fit in a dual points dizzy, doesn't line up at all.  

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Mechanically, that's not how it works. The 4-lobed cam on the dizzy shaft opens the points at (roughly) the same time. Since the points are roughly opposing each other, the opposing lobes open the points arms. The relay either opens or closes the electrical connection on the grounding wire to the retarded set of points. That's how it activates and deactivates the phase timing.

 

So the Pertronix won't "line up." You mean won't line up with the existing tapped holes where the points mount? Why not just drill and tap new holes in the breaker plate? It doesn't seem like that big of a deal.

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All I am saying is turn your motor with the dizzy cap off and see what happens.  On mine only one set of points ever opened which would make that set the primary no?  And I don't remember what else didn't 'fit' with the pertronix but I seem to remember the magnet collar thingy not fitting right.

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All I am saying is turn your motor with the dizzy cap off and see what happens.  On mine only one set of points ever opened which would make that set the primary no?  And I don't remember what else didn't 'fit' with the pertronix but I seem to remember the magnet collar thingy not fitting right.

 

I did when I had my dizzy out a few days ago to free the stuck pedestal. Both points open at the same time.

 

If one of your points wasn't moving, something was either wrong with it, or that sets of points was adjusted far enough out that it wasn't being contacted by any of the lobes. The points open and close mechanically. 

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Most Datsun 521 wiring diagrams, and the colorized one that is popular, do not show the additional wiring for the USA emissions add ons.

The primary set of points use the coil to point wire shown in the wiring diagram, black with a yellow stripe, you will notice on the wiring diagram, there is a small letter "A", for Advanced.

The secondary set of points uses a blue wire, with a yellow stripe.  The spade terminal on the distributor is also bigger, and and the external condenser is smaller.  The second point wiring is not drawn on the above wiring diagram, but looking closely at the distributor, you can see the points and the condenser for the second set of point are in the diagram, and has a "R" by it, for Retarded.

 

It was done for emission control.  It worked with the air injection system into the exhaust manifold.  It was thought that at very light load on the engine, the combustion temperatures were too cold, and the exhaust was too cold for any unburnt gasses to burn.  Retarding ignition timing makes the exhaust run hotter.

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It was the 1970's.

The biggest problems back then was unburnt gas, HC, evaporative, and from misfire, and CO, Carbon Monoxide.  Air injection helped both, but neede relative high exhaust temperature to work, this was before catalytic converters.

 

American emission controls seemed to be focused on percentage of noxious emissions, not on the total amount, that is grams per mile. 

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