Points Distributor governor springs (FSM conundrum)

[Careless]

Hey friends.

So I was finally putting in a new set of points for the Distributor I've restored and cleaned up... and while flipping through the FSM pages, I came across the distributor weight governor springs portion- and something is off here.

The distributor I have is an Emissions Control spec D612-52 model, as opposed to the D606-52. I believe it is the original one that came on this Jan 1970 car. They differ slightly, the D612- as far as I can tell, has distributor cap clamps that are two piece, and use a small bracket that holds them onto the body of the distributor- one of the small plated brackets has the cap alignment square that makes sure the cap only goes on one way- whereas the later style ones have it cast into the body itself (you could theoretically swap the two bracket positions and install the cap incorrectly on the one I have.

Anyways, that's neither here nor there, just a detail on the version I have to avoid confusion or if it relates to the issue I'm having:

The governor spring assembly...

On the spare distributor from the 71 (later style, cap can go on only one way) that I took apart to look at, the governor springs have two different tensions and are visibly different. This is indicated in the FSM:

 

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? 

I am new to points distributors so I am having fun putting it back together, but I'm not sure if it's going to work well. I'm going to try it with the oil ignition coil when I get the car started because I don't want to damage the NOS ignition coil.

 

 

 

Edited March 10, 2016 by Careless

[Chickenman]

The diagram looks right. The idea is that the lightweight spring is attached to the longer slot, and should pull the weights back all the way to the bottom of the slot at zero rpm so that there is no slop in the system. You bend the tang so that you have enough tension on the spring, so that timing will not start advancing until @ 1,000 RPM

At low rpm, the stiffer spring, should be floating free, you notice that it has an oval end that attaches to the tang. Initially, the LW spring controls advance, and it ramps up fairly quickly ( on Non-Emmissions or performace dizzy's ). Once RPM increases more the stiffer spring will actuate, and help slow the advance curve as centrifugal force is really flinging the weights out harder at higher RPM ( over 2,000 to 2,200 RPM Approx.

 

The important thing is too make sure that the LW spring is hooked up to the proper slot and tensioned just enough to pull the weights back all the way to the stop... but also to prevent the weights from advancing till about 1,000 RPM. Some guys set the tension too light, then the ignition timing will bounce around at idle, obviously causing an erratic idle and also losing overall advance. I set my timing at spec ( 700 to 750 rpm ) and check the timing mark with a timing light. Then I lower the idle to @ 500rpm and see if timing drops. If it does, then you have too little tension on the LW spring. Bend the Tang outwards to get a " little " bit more tension.

 

The heavy spring controls how quickly the advance curve reaches full mechanical advance. I usually like it to be " all in " by around 3,500 to 3,700 RPM. You can check. Adjust the tension on the Heavy spring tang to alter this rate. Note: Only tweak the Tangs a small amount at a time.

Note: The springs control the rate. The length of the slots controls the total amount of mechanical advance. Plate will be stamped with a number. IE: Stamp 7 = 7 distributor degrees or 14 crankshaft ( Timing mark ) degrees. An " 10" stamp would = 20 crank degrees. 

 

Jason Grey has an excellent article on tuning Datsun dizzys:

http://newprotest.org/projects/510/jasonGrayDistributor.pl

 

 

[Careless]

Good info, but I need to point out that my question is regarding the springs themselves- and not how they are set. I don't have two different springs in the D612-52 distributor. I will be using your tips to set it up and configure it once it's all together- but I need to know if the springs being the same is a normal thing...

Could the ramp-up you described on the Non-Emissions distributors be cancelled out by two same-part springs on the Emissions versions?

I am not sure if this is normal. It's never been taken apart prior to doing so myself. In the mean time, I'll see if I can get a photo of it later today. Gotta do some running around!

Edited March 10, 2016 by Careless

[CanTechZ]

The subject of distributors for the early 240z's does get a bit confusing, I don't have your answer but here is some more background info from a thread in 2009:

http://www.classiczcars.com/topic/31224-correct-early-series-1-distributor/?do=findComment&comment=278184

Here are parts book pages for the early version of D612-52 (part No. 22100-E4601) the later version of D612-52 (part No. 22100-E4603) the parts book makes no mention of D606-52, unlike the FSM. I noticed that the

later parts page notes "Set-Spring" whereas the early parts page does not.

FWIW, Mike

[Zed Head]

Check out the 69-72 TSB in the Downloads area - http://www.classiczcars.com/files/category/4-manuals/

I think that the light spring gives a faster advance, pegs out, then the heavy spring continues until it pegs out.  They don't show the springs but the curves (governor curves) have two ramps (see picture).

I've found that the data in the manuals often doesn't cover what's out in the world.  I have several 280Z distributors with 11 and 11.5 advance mechanisms,which would give 22 and 23 degrees of total centrifugal advance.  But there's no 280Z documents I've found that show either as a spec. 

[Careless]

8 hours ago, CanTechZ said:

The subject of distributors for the early 240z's does get a bit confusing, I don't have your answer but here is some more background info from a thread in 2009:

http://www.classiczcars.com/topic/31224-correct-early-series-1-distributor/?do=findComment&comment=278184

Here are parts book pages for the early version of D612-52 (part No. 22100-E4601) the later version of D612-52 (part No. 22100-E4603) the parts book makes no mention of D606-52, unlike the FSM. I noticed that the

later parts page notes "Set-Spring" whereas the early parts page does not.

FWIW, Mike

 

I'm glad you noticed this in the parts assembly- it's what I found in Nissan E-FAST as well. I see the exact same diagrams with the exact same nomenclature- which is actually what prevented me from following the FSM and taking the springs out of the spare 71 Distributor I also have (pictured on 50B-1 that you posted).

I said to myself... maybe I should see if anyone has run into this issue as well- Mainly because I noticed that most of the NOS distributors or ones available are not the style with the same cap clamps, so I knew something had to be off. Even the one mentioned as part of the reassembly procedure is not the cap clamp style that I have here.

Perhaps the best course of action would be to put it together as is for now, and set it up as if it were to be run as is with the current springs. I may have access to another early car very soon that I will be able to take a closer look at, and it will clear some of the air on this.

I wonder if there is an easy way to measure the tension on these tiny springs without breaking them. 

 

Now... the one thing that I'm curious to know is... if these springs are the same for the early D612-52 distributors, does the orientation of the spring matter? The ends LOOK somewhat different, but they don't have a long uncoiled leg side and a short side like the ones mentioned in the FSM reassembly procedure.

 

So many unanswered things. (Kinda enjoying it, though).

Edited March 11, 2016 by Careless

[Chickenman]

8 hours ago, Careless said:

6 minutes ago, Careless said:

(Snip)

Perhaps the best course of action would be to put it together as is for now, and set it up as if it were to be run as is with the current springs. I may have access to another early car very soon that I will be able to take a closer look at, and it will clear some of the air on this.

I wonder if there is an easy way to measure the tension on these tiny springs without breaking them. 

 

Now... the one thing that I'm curious to know is... if these springs are the same for the early D612-52 distributors, does the orientation of the spring matter? The ends LOOK somewhat different, but they don't have a long uncoiled leg side and a short side like the ones mentioned in the FSM reassembly procedure.

 

So many unanswered things. (Kinda enjoying it, though).

Good info, but I need to point out that my question is regarding the springs themselves- and not how they are set. I don't have two different springs in the D612-52 distributor. I will be using your tips to set it up and configure it once it's all together- but I need to know if the springs being the same is a normal thing...

Could the ramp-up you described on the Non-Emissions distributors be cancelled out by two same-part springs on the Emissions versions?

I am not sure if this is normal. It's never been taken apart prior to doing so myself. In the mean time, I'll see if I can get a photo of it later today. Gotta do some running around!

Are you absolutely  sure it's never been taken apart in the last 40 years? How are you sure of that? Swapping springs out in the early days was a popular method of changing the curves and often different springs were tried to get the desired curve. . I've even seen BNIB  re-manufactured distributors ( and alternators and starters ) thrown together with a mish mash of parts. 

In the end, it doesn't really matter. You can make either type of spring work to give you the curve you want. Either the heavier weight springs with the oblong end or springs without the oblong ends on the heavy spring. You just try different combo's and check the curve with a dial back timing light or better yet a distributor machine. Check out old timer Drag shops for the distributor machine. I've used Chevy springs in Datsun distributors to tailor the curve to what I want. 

Of course, the other issue is that Datsun could have used two types of springs. The oblong spring is definitely a stock style spring. I've taken apart many Japanese distributors ( Datsun, Toyota, Honda etc ) and come across that style many times. But that doesn't mean that they didn't make a production change somewhere down the road and switch styles. Maybe someone was in there... maybe not. I wouldn't worry too much about it. Tune the curve to what you want with the springs you have.

BTW, you can also buy inexpensive spring tuning kits from Mr Gasket, MSD, Accel etc for Chevies that will fit in Datsun Dizzie's. Buy the early HEI spring kits. It will give you several springs of different tensions to play with, and you can bend the tangs to play with things. Summit or Jegs carry them.

 

 

 

[Careless]

I'll look into those spring kits, but I'd really like to just use the stock stuff if it's the right stuff.

Yes, I am assuming the the distributor has never been taken apart, but as far as I could tell when taking it apart, it wasn't in the greatest condition, and just look like it never even had the cap replaced. The rubber seals where the clamp brackets mount to were still there, and I just got the feeling that it was never touched.

I will be looking at the other cars when they come to see what I can find. If 3 cars with the same distributor have the same spring, then I don't think it would be merely a coincidence. You could buy 3 remanufactured distributor done by the same guy in the same large rebuilding service center and they'd probably all have different springs unless they were all done in the same month.

[Chickenman]

Can you take a picture of the dizzy cam plate and the slots. One thing I was thinking about is, if the slots are the same length or nearly the same length, then Nissan may not have used a spring with the oblong shape on that particular Model number. Also, if the springs are quite close in tension, the secondary spring may not have or need the oblong end. It's all about how they want to shape the timing curve.

Governor weight MASS also comes into play. Nissan used different part numbers with corresponding different Governor weights on different distributors. On GM dizzies, it is very common to switch springs, weights and Cam plates to get the desired curve. All can be mixed and matched and the aftermarket carriers a vast assortment of Cams, weights and springs for GM dizzies ( HEI mainly ) .

 

[Careless]

Good point, I never even noticed in the FSM diagram that the slot is longer on the Cam Plate. I was concentrating on the spring thing so much that I kept saying "What? what spring size? they're the same? Am I blind?! The hell is going on here?!"

I have a digital scale that I can use to test the governor weights and springs as well. I will do that. 

Perhaps in the next couple of minutes if what I'm doing right now doesn't take too long.

[Chickenman]

I'll be installing a fully programmable HalTech ECU on my 280Z soon(ish) One of the things I'm really enjoying is the ability to quickly tailor an Ignition Timing curve with 2D and 3D maps. No more muckin' about with hauling Dizzy's in and out, swapping springs, changing weights, filing slots and all that nonsense. Just a few keystrokes and you are done. Plus it is dead nuts accurate... every time.

[Careless]

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.