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Ignition Coil Location

Discussion in '365 GT4 2+2/400/412' started by Tojo, Jul 2, 2021.

  1. Tojo

    Tojo Formula Junior

    Apr 12, 2002
    429
    Sydney
    Full Name:
    Tim
    Among the many parts my car is still miss are coils and their mounting brackets. Mine is a twin distributor carbie car, and I’m wondering where on the firewall do I actually mount the brackets when I find some? Cheers


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  3. Bill26

    Bill26 Karting

    Jun 19, 2005
    209
    Australia
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    Bill Murdoch
    Tim, they are on a common bracket sitting on top of the passenger footwell, tucked up behind the battery, under the wiper motor. They face outboard with the tops tilted upward. The bases are close to the inboard edge of the footwell top.

    Very difficult to find a photo and the parts lists are no help.

    Regards

    WM
     
  4. raemin

    raemin Formula Junior

    Jan 16, 2007
    879
    Lyon (FR)
    Full Name:
    R. Emin
    Here is where my single coil is located. You obviously do not have the k-jet frame mount, but I presume your coils are more or less in this area...

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  5. samsaprunoff

    samsaprunoff F1 Rookie
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    Jun 8, 2004
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    Good day Tim,

    My car is not too far from me and so I will post some pics for you shortly.

    Cheers,

    Sam
     
  6. Tojo

    Tojo Formula Junior

    Apr 12, 2002
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    Tim
    Thanks for the responses guys. Bill, you're right about the parts list being no help and no pictures out there. Sam's photos will be very helpful I think
     
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  8. Bill26

    Bill26 Karting

    Jun 19, 2005
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    Australia
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    Bill Murdoch
    Sorry Tim - the coil tops point downward (towards the engine). Also, each coil has a red, square Magneti marelli ballast resistor mounted on it.

    Regards

    WM
     
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  9. samsaprunoff

    samsaprunoff F1 Rookie
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  10. Tojo

    Tojo Formula Junior

    Apr 12, 2002
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    Tim
    Thanks Sam. Between those pics and Bill's descriptions, I now have a good idea of what i need to find, and where to mount them. Do you think the coil brackets bolt straight through the fiberglass panel? Or is there some kind of metal support bracket riveted to the fiberglass as well? Cheers, Tim
     
  11. Bill26

    Bill26 Karting

    Jun 19, 2005
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    Bill Murdoch
    From memory, originally rivets backed up with washers, but I used mushroom headed cap screws, washers and nylocs when I refitted them.
    (Looks like my memory of downward facing coils is proved wrong by Sam's pics)
    Regards
    WM
     
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  13. Tojo

    Tojo Formula Junior

    Apr 12, 2002
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    Tim
    Thanks Bill, I'll look to something similar with anchor nuts then. A quick search online has revealed those ballast resistors are virtually unavailable except at crazy prices I'll be looking for some alternative options there too I think
     
  14. samsaprunoff

    samsaprunoff F1 Rookie
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    Good day Tim,

    You are most welcome! I will check on how the coils are mounted later today.

    Cheers,

    Sam
     
  15. samsaprunoff

    samsaprunoff F1 Rookie
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    Good day Tim,

    I am thinking out loud and so bear with me... If you modernize your ignition system then the ballast resistors may not be necessary and if so then to maintain the look you could easily 3D print some replicas. I have not spent a lot of time on the ignition system and so my comments may be incorrect... however, it may be worth investigating given your comments about the resistors being close to NLA. With that said if you keep the original ignition system, you could use non oem ballast resistors... and then keep an eye out for some originals?

    Cheers,

    Sam
     
  16. Tojo

    Tojo Formula Junior

    Apr 12, 2002
    429
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    Tim
    Interesting musings Sam, I've been thinking about it a bit the last couple of days. I plan to modernize the system with a hidden sparkrite box or something similar, but I want to keep the originality look too. I believe the correct coils are the same as used in the carbie 308's, and my parts guy reckons he has some good used ones I can buy from him. I also found this helpful thread, that I'm about to do some better research on. https://www.ferrarichat.com/forum/threads/whats-with-marelli-bk3a-coils.251593/

    As an aside Ferrari UK sell alternate coils to suit 365/400's for around $100gbp. No pic on the site, so I don't know what it is exactly. The original BK 3A coils would be $260gbp, and to buy it direct from Beilstein complete with bracket and ballast resistor for EU $396 https://www.bielstein.com/Ignition-Coil-BK-3A. Obviously worth the effort for a full on concours car or if you want Classiche certification. For your Boxer, I noticed in their photos the alternate for the original coil that Ferrari have listed is the Bosch Red coil. It can be purchased substantially cheaper at other retailers.

    I found one original Marelli ballast resistor on ebay for $70usd. Says it was for a Fiat 125/850 but it looks the same as the red one you have in your photos. I don't know what it's rating is, but, at that price It can serve as a good template to make a replica if needs be. Cheers
     
  17. Ak Jim

    Ak Jim F1 Veteran
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    Dec 23, 2007
    5,715
    North Pole AK
    #14 Ak Jim, Jul 6, 2021
    Last edited: Jul 6, 2021
    I used Pertronics pick ups in the distributors and also their matching coils and spark plug wires.
     
  18. raemin

    raemin Formula Junior

    Jan 16, 2007
    879
    Lyon (FR)
    Full Name:
    R. Emin
    On my other cars I've used some ignition booster with dwell management, works quite well with the stock points. There is no modification to be made to the distributor, and there is even a toggle switch that allows to revert back to stock ignition. It can operate with or without the stock condenser.

    On the plus side : no more need to replace the point since I installed it (45.000km): the only service I still perform (twice per year) is to clean the cap and put a drop of oil on the wig. The dwell management is quite obvious when cranking the engine.

    On the negative side : no significant performance gains under normal driving conditions. This was a DIY solution made by Perlor-Radio that I cannot find any-more as a kit. Other alternatives I've found so far do not provide Dwell management.

    As far as I know it is also possible to hack a GM HEI module and convert-it to a point booster.
     
  19. Tojo

    Tojo Formula Junior

    Apr 12, 2002
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    Tim
  20. samsaprunoff

    samsaprunoff F1 Rookie
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    Good day Tim,

    This looks to be very similar to what Raemin is using... and one cannot argue about the price (27.95 GBP)! Electronically, these units are pretty simple, but overall very effective. Essentially the box takes the brunt of the coil switching current which preserves the breaker points... but also allows a much more consistent and faster switching event. As Raemin noted, there would be no real performance gain, as the resulting spark voltage will be pretty much the same. However, it would certainly be an improvement over the stock system... and with virtually no breaker point wear so it would certainly reduce overall ignition maintenance costs dramatically.

    There is no question that a full migration to a new and modern ignition module would be the best solution, as it would offer more spark voltage (could be good or bad depending upon your wires, etc), more sparks at low revs (reduces fouling, quicker starts, etc), and would address the age/design issues of the original Marelli module. However, this approach certainly costs more and requires more effort to install... and so a cost-benefit analysis would need to be done to determine if it is worth pursuing.

    With that said the spark-box approach looks to be a very good bang for your buck and I cannot see any real downside in going with this solution.

    Cheers,

    Sam
     
  21. samsaprunoff

    samsaprunoff F1 Rookie
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    Good day Raemin,

    I fully agree and I think this is a great idea... it would certainly be possible to use a GM HEI module as a spark box and it would work almost identically. I would have to analyze the power dissipation of the module, etc as mounting the HEI Module to a heatsink of some sort may be required.

    Cheers,

    Sam
     
  22. raemin

    raemin Formula Junior

    Jan 16, 2007
    879
    Lyon (FR)
    Full Name:
    R. Emin
    In this case you can also use an HEI compatible (i.e more powerfull) coil, which is a definitive improvement over the "box" I am using. Together with dwell management that would be the best of both world: capacitive discharge ignition without butchering the magneti marelli distributor.

    The boosters do improve performance somehow. The spark duration is controlled by the dwell and the condenser. Unfortunately the distributor dwel induces a spark duration that varies depending on rpm, so the distributor has to be adjusted so as to find a proper compromise between low rpm and high rpm spark duration. The booster does not take these into account and will produce a "perfect" 1ms spark regardless of rpm. On my car it did improve cranking (i.e ultra low rpm) significantly. I presume the Ferrari distributor is optimised for mid/high rpm, so the booster will probably enhance low rpm ignition.

    You could also retro-engineer the DIY kit I am using in order to make a "single" booster for dual coil. High performance coil (1.5ohm) would be a plus : http://marchal.jean.free.fr/Montages/AllumageElectro.pdf (it's in French, but schema is page 2)
     
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  23. samsaprunoff

    samsaprunoff F1 Rookie
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    Good day Raemin,

    Thanks for the document/schematic. As I expected, the circuit is pretty straightforward and it uses a tried and true timer chip (Part number 555) in order to create a "clean" output pulse of sufficient duration. From the looks of it the pulse duration is fixed and so a compromise was struck between low and high RPMs, as you cannot optimize spark output for both instances. If it were me... and using today's tech... I would use a embedded microcontroller for spark duration/timing and have the duration based upon the engine RPM... which can be easily calculated by measuring the time of the breaker points are opening and closing. The result is that you could achieve an optimum spark output for all RPMs... or create multiple sparks at low RPMs, etc. Secondly, I would use modern switching devices to maximize energy transfer to the coil along with a much faster switch rate, and lower power dissipation... a win-win-win. Controlling two coils would also be pretty straightforward too. If I ever get out of my never-ending spare time deficit I will design up a modern replacement, as it would be a pretty straightforward to do.

    Overall, I think it is great that someone thought about this and created a nice design based upon the available tech at the time.

    Thanks again for sharing the info!

    Cheers,

    Sam
     
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