Points Distributor governor springs (FSM conundrum)

[Chickenman]

Digital scales won't help on th springs. On a spring that small, an increase in wire size of .001" to .002" will make a considerable difference in tension. You could use a small tension gauge, or just use the time old method of " sensitive hands " Pull the springs apart with your hands and you should be able to feel the difference in tension. If your hands are not that sensitive or the springs are really close in tension, hook the two springs together by the end and pull. The lighter tension spring will stretch further.

[Chickenman]

3 minutes ago, Careless said:

yeah i'm quite familiar with standalone engine management- but this is the first points distributor i've had to attempt to rebuild myself- and the car is being restored to its factory originality, so no room for EMS.

 

So you're new school learning old Tech.. and I'm old school learning new Tech ?

[Careless]

Just now, Chickenman said:

So you're new school learning old Tech.. and I'm old school learning new Tech ?

No one ever mentions it, but apparently you CAN teach a NEW DOG old tricks! 

[Zed Head]

By Nissan's methods of the time, you were supposed to test your distributor curve on a machine.  So matching spring appearances, or slots, or weights won't really get you there.  If you really wanted to you might find an old timey shop with a machine and take your FSM advance curve page over and have it replicated.  But the curves were designed for old timey gasoline, with no ethanol and with tetraethyl lead anti-knock additives.  So, aside from appearance, there's not a whole lot of point to building an exact old distributor and matching the old distributor curves.  

[Chickenman]

Sorry, ZH.. but I've still been tuning carburated cars with dizzy's for the past 40 years up to the present day, as well as EFI cars since 2006 and I have to respectfully disagree with you . The physics of the engines haven't changed.  Honda's V-Tech's  with 11 to 1 CR ratios STOCK and even most econo boxes with CR's over 9.5 or 10 to 1 prove that. While modern ECU's and knock sensors allow more aggressive timing curves, and allow the engine designer to run closer to the Maximum performance edge older cars can still run fine on modern fuels. Today's modern fuels aren't that bad and Ethanol is a BONUS for High Compression or Turbo cars. Ethanol ( even 10% ) allow more aggressive timing and higher compression or boost because it burns cooler in the combustion chamber. TEL octane enhancements have been more than matched by modern blends. It's just that a lot of refineries and places like California basically " mandate " lower Octane fuels. That being said. You simply Taylor the maximum mechanical advance to the fuel. The curve shape doesn't change, just the final numbers. I run an aggressive curve on my 280Z but with conservative final overall numbers. I get 25+ MPG and the car runs like a Bat out of Hell.

The old curves still work just fine. You may have to be a bit conservative with the overall numbers in California... but that's always been true.

Regarding Distributor machines, while nice, they aren't really necessary these days. Nissan didn't have modern electronic dial back timing lights back in the day. Dial Back timing lights can achieve exactly the same results as a distributor machine.

 

BTW... OP lives in Canada. Canadian fuel is well known to be of better quality that USA fuel. It's a difference in standards, for our extreme climates, which just so happens to effect High Performance cars in a positive way. In short both USA and Canada use AKI standrad which si R&M/2. But Canda refineries put more weight behind the RON values which has more effect on anti-detonation tha MON.  Turbo Audi/VW/Porcshe guys are all over this, and it's no small matter that two of the largest aftermarket tuners for German Turbo car are based in Canada ( Unitronics and Eurodyne ).

Edit: I live in Metro Vancouver Canada, and often travel down to the Sates. Used to Autocross down there a fair bit. So did a lot of my friends. On our Pony cars with carbs and dizzies we'd have to Detune are cars by about 2 degrees on overall mechanical advance to run on the same " Octane Rating " of fuel that we ran in BC. Today,  my Turbo Audi does that with automatically with a sophisticated digital ECU and dual knock sensors. I styill have to manually dial back the advance over optimum on my old 425 HP Camaro and even on my 1976 280Z. This was true in the 70's and it's still true today. You always tune to the fuel and conditions you use.

Edited March 11, 2016 by Chickenman

[Zed Head]

My point is that there is no point in going back to what Nissan did originally.  Points or pointless distributor.  There is no benefit.  The cost/reward ratio is way off.  The only reason to do it is to be able to say that it is just like the factory said they made it.

If you could dig back through your collection of information and show the advance curve for the D612-52  distributor, that would be worthwhile.  Then Careless might be able to get the parts to match the curve.  If you're not going to match the curve, then what are you doing?

Where do dial-back timing lights come in to the discussion?

[Careless]

10 hours ago, Chickenman said:

BTW... OP lives in Canada. Canadian fuel is well known to be of better quality that USA fuel. It's a difference in standards, for our extreme climates, which just so happens to effect High Performance cars in a positive way. In short both USA and Canada use AKI standrad which si R&M/2. But Canda refineries put more weight behind the RON values which has more effect on anti-detonation tha MON.  Turbo Audi/VW/Porcshe guys are all over this, and it's no small matter that two of the largest aftermarket tuners for German Turbo car are based in Canada ( Unitronics and Eurodyne ).

I live in Canada, the car is here- but it will be transported to California later in the year when it's done.

[Careless]

9 hours ago, Zed Head said:

My point is that there is no point in going back to what Nissan did originally.  Points or pointless distributor.  There is no benefit.  The cost/reward ratio is way off.  The only reason to do it is to be able to say that it is just like the factory said they made it.

If you could dig back through your collection of information and show the advance curve for the D612-52  distributor, that would be worthwhile.  Then Careless might be able to get the parts to match the curve.  If you're not going to match the curve, then what are you doing?

Where do dial-back timing lights come in to the discussion?

Zed Head, excuse me for sounding like a jerk- but the point of this exercise IS to say that it's exactly how the factory made it, because that's what my client/employer asked me to do- so that's what he and the vehicle will get. If the parts that I seek were not in usable condition or not available new if they were damaged- I would look at getting a spare dizzy and swapping the parts over, or going with the HEI replacement springs as an option that was recommended previously.

There is no difference in cost/rewards ratio- in fact it would cost me more to use springs and a cam plate from a later style car because I would have to buy all those parts. My point is, if the springs that came in the original distributor are the same in size and shape as the ones that I have seen in there (which it seems to be leaning towards), then I don't need to get any parts, and I will assemble it as is- and it's just another true-to-form detail that the car has- which both I and the owner will know about, and that's that.

It would literally take more work to find springs, cam plate, and weights and put it together and adjust it than it would to come here and ask "are these springs supposed to be the same. because if it's supposed to be like that, then it's a restored and completed part".

That's why I did it. It has nothing to do with gaining performance in any regard. 

Edited March 11, 2016 by Careless

[Zed Head]

23 hours ago, Careless said:

On the distributor I've rebuilt, the springs are the exact same, and there is no difference between the two, except for #3 and #7 in the diagram- the circular end and the rectangular end. while situated at top dead center (on a bench, mind you)- I put the cam plate in and verified that everything looked like the photo shown, even the small start/end advance angle gap on #2... but the springs are still bothering me.

Is this part of the reason why they were "Emissions" style distributors? They didn't advance the gap due to offset weight distribution? Should I be concerned? 

Actually, I thought I was sounding like a jerk.

I almost put the phrase "unless you're building a full-scale model of a car" but thought it sounded wrong.  But, that appears to be what you're doing, in essence.  So, the discussion about performance and the reasons for Emissions distributor differences are kind of irrelevant.  But, matching the advance curves of the distributors, past and present, using a machine DOES confirm that you got the parts right.  If the parts you put in don't generate the same curve, how can they be considered the right parts?  Studying the curves, if they're available, can also tell you something about the springs used.  The two slope curves must be produce by two different spring rates.  If the curve for the D612-52 is single slope then the springs must be identical.  So that's a clue.  

I was just trying to get to the basic point, and help you get there.  I copied your original question just to get back there.  As Chickman pointed out, the distributor may have been messed with over 40 years, and I also mentioned, what came over on the boat may not match what Nissan described in the Service Manuals.  So you kind of have to decide what you're reproducing, the intent or the reality. 

Anyway, plenty of information here.  A plot of the D612-52 curve would be great, if anyone has one.  Alright, the coffee's wearing off now.  Carry on.

[Careless]

Two more cars are coming, and they might have the same distributor. If they do- I'll take them apart to assess the springs. If they are the same in dimension and look, I don't think it will be coincidental. I know it's not the best test- but it's good enough for me until I get the car running. If it runs well and doesn't operate funny, then I'll be happy with it.

 

Currently I'm happy with how it looks- its just the internals that I need to figure out :-D

I have a feeling the distributor clasps are supposed to be black though, but having them plated doesn't hurt. Can always be painted overtop :-)

 

Edited March 11, 2016 by Careless

[Patcon]

Looks beautiful, as always...

[Chickenman]

Beautiful restoration. Yes the clasps that attach to the distributor were usually Black. The small bracket that screws to the Dizzy body is Cad color.

I'll try and find some specs for the D612-52. I have some old books kicking around.

 

Regarding the actual timing curve and numbers. If the engine is stock, you should have no trouble running on the figures that Nissan originally used or the numbers I gave you. On California 91 Octane fuel.

Nissan was actually pretty aggressive back in the day with how quickly they ramped up the curves. However, they did not run as much total advance as was optimal ( for maximum performance. This was mainly for emissions specs, as cars in the mid-70's usually ran with less total timing in an effort to reduce NOX emissions. It made for inefficient engines with low power. They also had to be conservative as they had to allow for consumers occasionally putting in regular fuel instead of Premium.

Here is an XLS of some of the distributor curves. Note how Nissan reached full mechanical advance fairly quickly, but limited the total amount. Bear in mind that these tables do not show the compression ratios of these cars. That must be considered when comparing Emissions and non-emissions timing curves.

Distributor advance curves.xls

Edited March 12, 2016 by Chickenman
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