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Ignition facts ??

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

  1. I redid the dynamic compression test, my method was flawed. The test result numbers in the previous post should be .
    Cranking - 168 average
    Running - 89.3 average
    Snap wot - 125 average..

    Based on the "about 50% " of cranking I should be running at 84 average.
    My test shows 53% 89.3

    And based on 80% I should WOT at 134.
    My test shows 74% 125

    I suppose my intake is a ever so slight restriction ?? Would that be correct ?
  2. flat34pu
    Joined: Jun 9, 2007
    Posts: 453


    great info.
  3. ago
    Joined: Oct 12, 2005
    Posts: 2,199

    from pgh. pa.

    So I take it, an Anolog MSD box doesn't do much? It seems the failure rate of these boxes is higher than stock ignition.

    Joined: Jun 3, 2005
    Posts: 8,210


    I'm going to throw a head-spinner into this topic. 1930 Packard 8, then 1932 8 cylinder cars, both with dual point Northeast distributors. The earlier cars had 1 coil, 2 points, both sets of points opening at the same time (?). Later, 2 point sets, 2 coils, actually fairly easy to set and really easy to understand. In the early models with one coil, both breakers had to open simultaniously. If one was off just barely over 1 degree it would lose power and backfire with no set frequency (you never knew when it would screw up, it just did). Absolutely would not run well enough to drive with only one set working. That particular job didn't offer the luxury of a full investigation due to time restraints so I just set it up to perfection, even allowing for take-up in the distributor drive. The customer's response was "How did you 'hop up' my car? It's so fast and smooth now."

    The twin coil/breaker deal is really easy to get your head around as there's 2 marks on the damper to set things to. We won't clutter this up with that one just yet, but set up right you can litterally balance a nickle on end with the engine running. Of course idle mixture and fan blade air path has something to do with the nickle's ability, but it's always a good final "test".

    Quick edit, I forgot to actually ask the question, why 2 sets firing simultaniously? I don't have tech manuals that far back so if you have any ideas...
    Joined: Jun 15, 2006
    Posts: 3,385


    Pontiac Spec Card :::1968 428 High Po 390 HP

    Attached Files:

    Joined: Jun 15, 2006
    Posts: 3,385


    OK, after almost 100 posts the subject is still right on !
    Lets use a 1968 Pontiac Spec card from Sun Electric to kinda wrap up the basics etc:
    Load the card from above and lets study it a bit per the above discussions and questions.

    Starting at the top left.
    Compression ration is 10.75 to 1 ( almost 11) and compression is 185-210 psi.

    Cranking voltage is 9.0 volts minimum.

    Contacts are adjusted for a 28-32 Degrees with a allowed 2 degrees of variation.

    Ignition timing is 9 degrees BTDC at idle...

    Combined vac and mech advance is 31.5 to 35.5 degrees
    Cent only is 11.5-15.5 degrees

    Interesting number as this would be the max setting the engine would ever want or need regardless of the modifications etc...

    Fuel pressure is 5-6 PSI at 1000 rpm.

    Spark plugs are AC44S with a .035 plug gap and are torqued to 20 ft lbs.

    Distributor uses a 60 psi oil pump spring.

    Another interesting number as the oil pump is driven by the distributor, high pressure oil pumps cause extra drive torque and wear !!!!!

    Delco distributor

    Condensor Capacity is .18-.23 MFDs

    Mechanical advance is all in at 2300 rpm with a max of 11 degrees
    ( 22 degrees engine)

    Ignition coil primary resistance of 1.81 to 2.01 and ballast resistor a loom ( calibrated wire) of 1.80 ohms

    Note that the primary resistance is approx 4 ohms which is pretty typical for a contact system..

    A lot of information on this single card for sure ..
    Joined: Jun 15, 2006
    Posts: 3,385


    To answer one more question before i attack a huge pile of distributor work for the day, someone asked about vacuum advance and the hook up.

    In most cases vac is hooked to the manifold vacuum direct.
    However there have been many over the years that use venturi ( or ported ) carb vacuum for emission reasons etc.
    For our discussion lets use a direct vacuum hookup.

    Looking at the pontiac spec card we show a spec of :

    Total spark advance of 35 degrees
    and Mechanical/centrifigual of 22 degrees engine
    and vacuum advance of 20 degrees.

    Added together they would total 42 degrees , however this wont ever happen and when vac is high ( 20 degrees , mechanical (rpm) is low maybe 15 degrees = 35 total.

    OR rpm could be high and mechanical is 22 degrees and vac is low with 13 degrees = 35 total

    Mechanical and vacuum overlap each other to provide the spec advance all the time driving down..
  8. This is one of the most informative threads I have read. Thank you!
    Joined: Jun 15, 2006
    Posts: 3,385


    Think about it this way.

    The addition of the red box takes the load and current flow away from the contacts. Kinda like a relay that the contacts control. They were operating at a current flow of 4 amps and now use only milli amps. Thats a good thing.

    The bad issues start when the MSD uses a very low resistance coil and starts using 8-10 amps in the box circuit, then you have a higher failure rate.
    Just the heat build up alone is fatal to some of the parts etc....
  10. Cantstop
    Joined: Jul 11, 2005
    Posts: 239


    Awesome info...can't wait for the rest...........
    Joined: Jun 15, 2006
    Posts: 3,385


    Time for some more discussion;
    Some of the subject matter can be further explored by using and google.
    We have discussed voltage and voltage levels in the ignition system now lets add "coils" to the discussion.
    Ohms law falls into place here with volts ( pressure) , amps ( flow) and resistance (resistance to flow).
    Another one to think about is "watts" Watts is electrical horse power.
    Volts x amps = Watts.

    Example one would be 12 volts flowing 4 amps would equal 48 watts.
    12 volts flowing 10 amps would equal 120 watts...
    In an ignition system if we want "more" output we would want more watts. You would need to increase the voltage (used in a capacitive system), increase the amps ( use lower resistance coil).

    We have three coils made for us at Andover coil company in Layafette Indiana, each with a different application. ( all old school oil filled)
    1= 3 ohms unit = Used for dual coil systems and four and six cylinders.
    2= 1.5 ohm unit = Used on most V8 applications with a 1.5 ohm resistor.
    3= .5 ohm unit = Used with high energy ( with current control) like the GM HEI module etc.

    Our most used coil is the 1.5 ohm with a 1.5 ohm resistor. Divided circuit 1.5 and 1.5 allows the coil to run cooler .

    Heres a couple pictures:


    Andover coil made for the Delco folks a few years back..


    A coil i put in a mason jar to display and open and close the container for scope testing at various points.


    A "exploded " coil from a customer that left the battery charger on all night with the key on. Oil got hot enough to expand and blow the seals out....

    Our coils are a 100 to one ratio meaning the secondary is 100-1 winding comparing the secondary to the primary windings. This is a pretty typical stock ratio that runs the engine very well. Rating is 25,000 to 30,000 volts. ( remember 30,000 is more than enough for most vehicles as we actually need much less properly tuned with a somewhat normal compression ratio)

    As we go thru this discussion we will build larger output coils and talk about the whys and when we might actually benifit from the higher outputs...
    Last edited: Nov 8, 2012
  12. Very interesting . Bubba !
  13. revkev6
    Joined: Jun 13, 2006
    Posts: 3,351

    from ma

    which is why MSD has recommended coils for these boxes I take it... I have two MSD6al boxes that I ran in VW engined midgets (one as a spare). I ran these boxes for three 22 race seasons without a failure using a complete MSD setup. electronic dizzy, msd recommended coil and the box.

    this was going to be my next question and it seems you are heading in that direction!! what coil to use where!! LOVE THIS THREAD.
    Joined: Jun 15, 2006
    Posts: 3,385


    One more coil made here in Indiana for one of my racer friends This works with a magneto (external ignition coil) on sprint cars....
    Could ( left uncontrolled) need hundreds of amps to drive it and weld thru the frame on the car if needed to. I will provide some more specs as time and testing permits...


    I would just call it "the stun-er" for now , cant imagine being hit with a couple sparks from this dude.
    Will work on coil applications this week end....
    Joined: Jun 15, 2006
    Posts: 3,385


  16. Bugguts
    Joined: Aug 13, 2011
    Posts: 704


    Subscribed! Thanks for all this work.
    Joined: Jun 15, 2006
    Posts: 3,385


    Ok its monday , snowing lightly in Indianapolis. Looks like i am behind approx 70 orders with distributors and i have this oinched nerve deal going on in my lower back. Surgery is scheduled for Friday afternoon ( hope this gets over with soon) and just plain old dont feel like doing much this morning.
    So i guess we need to get this coil issue behind us....?????:eek:

    A little coil review , the ignition coil is really nothing other than a electrical transformer stepping up the low primary voltage 12-14 volts ( could be 200-300 when firing will discuss later) to approx 20,000 volts if needed.
    Transformers may be tapped ( secondary ties to primary winding , requires no ground) or untapped ( later model units that didnt wish this extra inductive kink to be uncontrolled). The transformer size may also vary with a turns ratio based on needs etc. ie : big - little etc
    The discussion in my world always needs to start with "stock oem configuration" as most problems can be fixed by just using the factory setup. Flathead ford engines are a good example, the engines seldom use a low to compression and the design of the engine doesnt need the huge increase in spark out put wanted by many engine builders. A good reliable spark is what we are after in what i will call the " stock -level one " spark .
    The factory flathead also has a design limitation with the factory distributor that may or may not offer the correct spark advance etc. But thats a distributor issue NOT a coil problem.!!

    So lets stop for just a minute and consider that the ignition system is "as designed " from the factory. If using a spec chart like we showed above , use the highest level of horsepower the engine developed for a given year etc. So we now have a good condition engine, with correct spark cables, good condition distributor ( clean and lubed) and working like it was designed.

    The ignition coil for this application would be a typical 1.5 ohm primary resitance and 25,000-30,000 volt out put rating. The spec sheet from would look like this ...

    Mallory 29219
    Coil Style:Canister
    Primary Resistance:1.400 ohms
    Coil Internal Construction:Oil-filled
    Coil Color:Chrome
    Maximum Voltage:58,000 V
    Turns Ratio:112:1
    Secondary Resistance:10K ohms
    Inductance:6.6 mH
    Peak Current:180 mA
    Spark Duration:300 uS

    This would make a good replacement ignition coil for a stock resistor type ignition system......

    THEN we move up a notch to another coil:

    MAS blaster 2 #8202
    Coil Wire Attachment:Female/Socket
    Coil Style:Canister
    Primary Resistance:0.700 ohms
    Coil Internal Construction:Oil-filled
    Coil Color:Red
    Maximum Voltage:45,000 V
    Turns Ratio:100:1
    Secondary Resistance:4.70K ohms
    Inductance:8.0 mH
    Peak Current:140 mA
    Spark Duration:350 uS

    Looks good but in reality is a bad choice for a stock replacement as the .70 ohms ressitance would require double the current for this application.
    A good coil but not our choice with out current , module etc circuit...

    Use the summitt web site and look up some of these units, pretty easy to buy the wrong ignition coil for a given application..........
  18. rhpope
    Joined: Oct 22, 2007
    Posts: 73


    Some questions on coils, primary resistance and application, or maybe just a confirmation of my understanding so far.

    Question 1:
    From reading all of this and from my own research, I think I understand that a points type system needs about 3 Ohms total primary resistance for long life of the contact points. That could be a combination of a coil with 1.4-1.5 ohms of primary resistance with approximately a 1.5 Ohm ballast resistor or a 1.5 Ohm OEM resistor wire in series with the coil. Or you could use one of the a 3 Ohm primary resistance coils that are readily available from the aftermarket or exactly like the Bosch coils there were used on air cooled VW Bugs. The VW Bugs were points systems that used a 3 ohm primary resistance Bosch coil.

    Question 2:
    What coil do you use with a Mallory Unilite module equipped distributor? I believe it is supposed to be a standard coil (points type) with 1.4-3.0 Ohms primary resistance. The minimum is 1.4 Ohms, but greater is better by adding a resistor up to 3.0 Ohms total to reduce the stress on the Unilite module. Less than 1.4 Ohms is bad and will significantly reduce the life of the Unilite module.

    Question 3:
    What coil should be used with an MSD 6 series ignition control box? For points I think it is just use everything original to the points system, but what do you use with either a stock electronic system or aftermarket system? I think the electronic/magnetic pickup system should be a 0.7 Ohms primary resistance coil and no additional primary resistance such as a ballast or resistor wire is necessary. Examples of the electronic system distributors would be the Ford DuraSpark and MSD billet with the same basic magnetic pickup design as the DuraSpark.

  19. So does PerTronix if that helps any :D
  20. Or, MSD likes sticking stickers
    Oh hell, I may have just hit a Hornets Nest
    Joined: Jun 15, 2006
    Posts: 3,385


    I will run some of these values with a current probe and lab scope to display some of these options next.
    Joined: Jun 15, 2006
    Posts: 3,385



    I have a section for PerTronix coming soon. They have a special section as well..:D
  23. Back when I was setting up distributors for racers I had a Sun distributor machine.
    A good single point distributor with only minor changes can rev to over 7,000 rpm WITHOUT point bounce. I used stock coils and soild core wires with non-resistor plugs (J - gapped). I used point distributors for 15 years in my own race cars until I was handed a Delco HP HEI unit from a sponsor.
  24. Thats all I run in my 56. My distibutor by the way. Mallory dual point with primary points removed :eek:
  25. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,220


    When the maginatic field in the coil is collapsed isn't that at a given speed so how can you make the secondary spark longer?
  26. Thanks for sharing your knowledge. I had a good time reading for the last hour. Very helpful.

  27. lol, i'll be more then glad to show you some pictures on how our hvc series coils ( 8250-8252-8251-8253-8261)are all hand made...( nothing to hide)....

    <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p> bobbin machine.gif

    2012-11-16_08-58-06_800 (2).JPG


    8253 part2.gif

    hvc 2 coil 8253.gif </o:p>

    <o:p> </o:p>
  28. and here is a coil current chart .

    i'm sure the guys /gals at pertronix have similar info on there stuff too.
    coil current-hamb.gif

  29. with oem and aftermarket coils?

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