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Ignition facts ??

Discussion in 'The Hokey Ass Message Board' started by GMC BUBBA, Oct 22, 2012.

    Joined: Jun 15, 2006
    Posts: 3,385


    Ignition “needs”

    Can we talk ???
    Part 1
    I get this phone call each and every day.
    Goes like this :

    Jim I have a xxx engine going in a hot rod build up and I need hotter spark !!

    Q=Well why would you need hotter spark ???
    A= Well I have a xxx engine and three carbs with a 505-43xd2 camshaft in a 1927 Ford T coupe
    .Q= That sounds cool what rear axle do you have ?
    A= Beats me came out of a Ford truck of some kind.
    Q=Is the car running now ??
    A= No I am just putting it all together .

    Now lets come up with a group answer to all the above.

    99 % of the time you don’t need hotter spark you just need reliable steady spark. In most cases a stock ignition system tuned will supply more spark than you would ever possibly need.
    A good example would be a standard Delco ignition system on lets say a 1968 350 Cubic inch engine with a four barrel carburetor. The stock coil has a max output of 20-25,000 volts and the engine on a good day needs approx 5-8000 volts to ignite and burn the air fuel mixture. Accelerated to mid range of 3000 rpm with a load the ignition demand might jump to 10-12,000 volts leaving a reserve of approx 15,000 volts.
    This reserve would allow the ignition to function ( in stock form) for a long period of time or a lots of miles etc.

    A couple of ignition facts:

    1= If a stock ignition system was using 6,000 volts at idle with a stock ignition coil and we stopped and changed the coil to a Super stock 40,000 coil and retested , the engine would still need and use 6,000 volts.
    The only reason for a larger output coil is to increase the reserve voltage if ever needed.
    2=A hotter spark and bigger coil wont fix a over rich fuel mixture..

    Reasons for the need for larger reserve voltage in Can We talk part # 2 ….Stay tuned…
  2. junk yard kid
    Joined: Nov 11, 2007
    Posts: 2,719

    junk yard kid

    The suspense is killing me. Is it resistance from worn parts, air fuel density, or heat? Larger gap?
  3. KoolKat-57
    Joined: Feb 22, 2010
    Posts: 3,032

    from Dublin, OH

    That is very, very good information!
    As is indicated by the phone calls you are getting and ?s on this board there are a lot of misconceptions as far as ignition, carburetors, camshafts, exhaust, etc.!
    Thankyou for your expertise and willingness to share your knowledge with us.
    Now if the good folks will read it and take it in, and use it, we will have a winner!
  4. Truckedup
    Joined: Jul 25, 2006
    Posts: 4,070


    This is what I know from experience;A longer spark duration can help.Magneto advantage is a longer spark duration......And aircraft ignition man told me that's what mags are used in aircraft piston engines. I always wondering when racing British cycles how that feeble spark for the magneto could fire 11-1 compression at 7000 was the long spark eventually get the fire going....

  5. inline 292
    Joined: Aug 25, 2006
    Posts: 296

    inline 292

    Subscribed - Your posts are always educational. Thanks for sharing your expertise with all of us.
  6. silent rick
    Joined: Nov 7, 2002
    Posts: 4,288

    silent rick

    ooh, ooh, i know.

    it's when you have an xxx engine and FOUR carbs with a 505-43xd2 cam going in a 27 T coupe:)

  7. depends on the magneto.
    Joined: Jun 15, 2006
    Posts: 3,385


    all of the above with some additions.........i will use your post for the outline on the next one......
    Last edited: Oct 22, 2012
    Joined: Jun 15, 2006
    Posts: 3,385


    Actually a magneto ( like a Vertex) doesnt have any more or less duration than a regular ignition.
    The degrees of rotation are still the same and the mag has to change each cylinder from positive to negative every firing period to boot. 4 cylinders fire positive and the other 4 fire negative polarity.

    Plug gaps in a mag are closer together ( .012-.025) however the primary voltage is much higher ( and gets bigger with rpm) giving us a much larger current spark output. The hottest of the hot....:eek:
  10. Well that's it then. My mind is officially BLOWN! :eek: I've got a fair grasp of points type ignition. I could fudge my way thru HEI if I had to. But I'm gonna have to do some studyin' up on this whole magneto thing! :rolleyes: Are you saying that the primary circuit flip-flops between positive and negative polarity?

    The higher primary voltage providing higher secondary voltages? :confused:
  11. H.G. Wells
    Joined: Mar 11, 2006
    Posts: 386

    H.G. Wells

    Great info.
    Major on the majors and minor on the minors. And I bet the calls looking for hotter spark are running on old crusty wires too.
  12. BabbitBeater
    Joined: Aug 18, 2009
    Posts: 160

    from Colorado

    Crap... now I have questions about stuff I didn't even know I didn't know...

    I'm subscribed. Thanks for sharing your knowledge. Are you still running a university out of your shop?

    Sounds like a dream vacation...
  13. Domino
    Joined: Jul 2, 2009
    Posts: 523


    Okay, I am in. school me sir.
  14. i'm just going to stick my fingers in my ears and wait until i call you about my Grant/spalding distributors
  15. FityFive
    Joined: Aug 9, 2010
    Posts: 314


  16. Willy301
    Joined: Nov 16, 2007
    Posts: 1,426


    I have to share, got a call today where the guy wanted to make more horsepower, but was not prepared to upgrade his cam, heads or rotating assembly. He wanted to increase his horsepower by changing from his aftermarket "in the cap" coil to a stand alone coil.
    His explanation: His "in the cap" coil only generates 42,000 volts, and he was told that they lose output when they warm up. Not get hot, but warm up...
    fiftiescat likes this.
  17. mynode
    Joined: Sep 22, 2012
    Posts: 25


    You're not saturating the coil at high rpm because the dwell time isn't sufficient so your coil is generating a lower voltage at high rpm than it does at idle.
  18. damn - when you right...your right.....kinda like "I need a bigger carb" .....
  19. Hot igntion has been a suckers deal since cars were first on the road. For some it is a temptation almost impossible to resist. I am glad someone finally stepped up to the plate and debunked it.
    You have my support.
  20. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,514

    Rusty O'Toole

    Years ago I read an interview with Smokey Yunick regarding his stock car racing hop up tricks. He said the one thing he couldn't improve was the stock ignition at least as far as making a hotter spark. Change the timing, advance curve ok but the stock GM ignition was fine. This was 1959 when he was working on Pontiacs. The electronic ignition they came out with in the seventies is even better.
  21. Truckedup
    Joined: Jul 25, 2006
    Posts: 4,070


    Bubba,thanks for correcting my misinterpretation of the magneto spark duration....
    I have a technical article on aircraft and cycle magnetos written by Kevin Cameron.It's a bit lengthy for this forum.You may find it interesting.... Discussion on capacitive/inductive magneto spark..I can email mail a scanned copy if you like.
    Joined: Jun 3, 2005
    Posts: 8,210



    I'll leave it to GMC Bubba to explain.
  23. hotrodharry2
    Joined: Nov 19, 2008
    Posts: 689

    from Michigan

  24. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,900

    dirty old man

    Joined: Jun 15, 2006
    Posts: 3,385


    Would love it , send to
  26. saltflats
    Joined: Aug 14, 2007
    Posts: 10,727

    from Missouri

    I have read an advertisement for a electronic ignition system some time back and thay said it has the accuray of points. ???? So why bother?
  27. revkev6
    Joined: Jun 13, 2006
    Posts: 3,351

    from ma

    so you basically want to make it a mallory double life?? :confused:
  28. johnboy13
    Joined: May 1, 2007
    Posts: 1,073


  29. you cant, ....with the 4 cylinder trigger will only fire every 90 degrees
    versus firing every 45 degrees that is required for a 8 cylinder .

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