Ignition Distibutor Questions

Rob Gaskin

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I have a few questions re my 240 distributor.

It is numbered D609 - 56A, 503 is that correct.

I have two other distributors D609 - 56A, 208 and 1202 are they 240 items?

My car runs-on quite badly, have checked the timing today and it is 18deg static at 800rpm. The car was not timed static but on a rolling road to give max power, think it is 35/36' max advance.

So how do I get a bigger advance curve so I can set the static lower and still get max advance ok. FYI I don't run the vacuum advance and have a Lumention unit.

When looking at the 'weight springs' they are different, one stronger than the other is that correct? My other two distributors only have one spring in them :unsure:. Can I take a spring off to give me more advance?

I realise this is all hit and miss and long-term I should get a dissy built to suit my car, any recommendations. How is the curve worked out to suit my cam etc.

Will a good old 280 dissy give me the advance I need and save a lot of aggro?
 

Mr.F

Inactive
1. Original points type distributors are not good at maintaining accuracy of ignition timing at high rpm
2. I'm pretty sure they should have a spring on each weight - your one spring distributors have lost a spring at some time, unless someone thinks having an uncontrolled weight is somehow good for advance - sure would come in quick though. New springs are no longer available as far as I am aware. Nissan Motorsport used to supply optional cam assemblies - OEM is quoted at 6 degrees and the option at 12 degrees. They also used to offer a solid distributor plate to eliminate the vacuum advance - useful for triple carb set-ups where the vacuum signal is compromised by the manifold design in most cases.
3. The Euro 240Z distributor is described as D606-52. Regarded as having a slightly quicker advance curve. D609-56A is listed for the Australian market in my parts book, but may have been common to Europe later on. There is also a similar looking Mitsubishi distributor 317-031 which may have been fitted as an alternative part.
4. Eight different Hitachi distributors are listed in the Engine Manual: D606-52, D609-56, D609-56A, D609-61, D609-62, D612-52, D614-51 and D614-52. The specs show varying vacuum advance and centrifugal advance characteristics for each one!
5. The 280ZX distributor is widely acknowledged to produce a good fat spark with excellent stability to higher rpm - better than the standard points type. The EFI Service Manual identifies three types up to October 1981: D6K7-02, D6K7-04 and D6K8-02 each varying in vacuum advance and centrifugal advance characteristics. Generally accepted is that the distributor from the facelift 280ZX is good for a couple of extra horsepower at least...I think (someone check?) this is designated D6K81-01.
6. For fanatics with money wishing to experiment, the Mallory Dual-Point distributor is available again and this provides adjustment of both vacuum and mechanical curves for optimum tuning. The dual points add stability to the shaft, eliminate points bounce and help to increase coil output to produce a fatter spark. Mallory also do a fully electronic version, the Unilite, also with full adjustability.
7. Electronic distributor spark can be enhanced with multiple spark discharge systems like MSD 6AL or the Crane Fireball Hi-6 series.
8. Or you could just give up on distributors altogether and implement a crank trigger programmable system with multiple coils...
 

Rob Gaskin

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Thanks, great info Mike. I don't use points but Lumenition Oprtonic system and the dissy is in good condition.

Yes having one spring seems dodgy but the weight would be controled in a fashion by the one spring - through the slotted plate that joins the two weights and cam post.

I mentioned I have different strength springs, not sure if this is normal as my other dizzies just have one like the weakest in mine. I think as a first test I'll but it back together as is, measure advance across the range and then try the different spring to see the effect. And also try my current set-up at a reduced static setting to see where/if the run-on stops

I bought a spare 280ZX engine a long time ago and it had a dizzy stuck in, but with points:eek:. Someone had obviously got there first and taken the electronic one. :devil:

PS I'm very happy with the performance and flexibility but if it should be less advanced at low revs I need to fix it.
 

Mr.F

Inactive
From the specs I have I think the total advance comes in quite early anyway...

Perhaps one spring is a way of increasing the speed at which the advance comes in. The unsprung weight will just fling out to the casing anyway...
Also, total centrifugal advance may exceed design specification with one weight, although your figures are suggesting that all is well. 18 degrees BTDC initial plus 18 degrees centrifugal matches the 36 degrees suggested.
Service manual for a 240Z distributor suggests 17 degrees BTDC initial anyway (as long as quality fuel is available)
 

Rob Gaskin

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Fitted it back together and did a test 500 - 4000rpm. Made a mark at 20btdc on crank pully so when the tdc mark passed 20 deg I just added 20 to the new mark. So if my new mark was at 10, I had 30 deg advance. Mirror taped on steering wheel so I could see rpm from front of car, throttle adjusted by central screw.

Pictures show unequal springs and the fact that the two weights work together on the slotted plate. Note the plate has unequal slots too (as do my other dizzys). Second picture shows me pushing a weight with a screwdriver, it will not travel anymore due to the second weight at full movement stopping the plate revolving further.

My timing is now:

500 14 deg advance
800 14
1000 14
1500 16
2000 19
2500 23
3000 27
3500 31
4000 35 full advance reached.

Interesting, it looks good to me, nice gentle progression. Just need to road test now.
 
Last edited by a moderator:

Nigel Brook

Well-Known Forum User
Rob: My D606-52 only has one spring and the slots in the plate are flat ended at both ends which suggests to me that your plate has been modified by filing the slot ends to give more advance which is what I did with my old L4. Could it be this has been done to modify your non-euro dizzy to euro spec? I have a complete non-molested D606-52 if you want to play about with the bits FOC.
 

Rob Gaskin

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Staff member
Site Administrator
Thanks for the offer Nigel, I would like to try your complete distributor please. I can easily fit my baseplate with Optronic bits and compare the two. Please PM me with your phone number, thanks.
 
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