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Ignition facts ??

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

  1. Lazy Jake
    Joined: Feb 4, 2008
    Posts: 59

    Lazy Jake
    Member

    Can these parameters be measured by an amateur hot rodder in his modestly equipped shop using an inexpensive VOM? I mean, can I test that coil I found under the jack stands beside my work bench before putting it on my 8BA? And, whats this about converting my Mallory dual point to electronic ignition? I have questions but, I am tuned in...

    subscribed...
     
  2. revkev6
    Joined: Jun 13, 2006
    Posts: 3,351

    revkev6
    Member
    from ma

    alright bubba, question for you. two spark options for me.

    I have an old mallory flat top dizzy. dual point, 4 lobe. appears to be NOS. I think it's a YC-310-HP off the top of my head.

    it will be going in a MILD 283. something like 8.5 compression. camel hump heads with a mild generic 80's "RV" cam. i am running an edelbrock 500cfm carb on a c4b intake.

    my thoughts on ignition were to run (and hide) a MSD 6al box that I have. From what i've read this sets the points up just as a trigger for the msd box. I figured this would make the distributor last longer?? not looking for performance here, just good stable spark without need to mess with points and condensers.

    my other option was just stick with the dizzy as is. I have a large can type condenser for it but it's probably junk and needs to be replaced with a smaller one. pros of this setup is I can run standard packard 440 wire, as I have no idea what I would run for a 7mm carbon wire with the msd box.

    thoughts either way?? I'm guessing from your article you feel there is nothing to be gained from the MSD box?? I was under the impression that the 4 lobe dual point dizzys had less dwell than a comparable 8 lobe??
     
  3. Home work assignment results
    All plugs in
    Cranking 158
    Running 85
    Snap 100-110

    This is a fresh chevy 307, 10.4x :1 compression XE 262 cam. Pulls 10" at idle

    All plugs out carb off the manifold cranking compression is 185.

    Current ignition system is-
    stock delco distributor, ( probably from a junk yard)
    Old unknown accell super stock coil 1840
    1.5 ohm ballast resistor fed by 12 volts no resistor wire , and no bypass wire from starter to coil
    AC delco r42ts plugs.
    7 mm wires

    I have an exhaust thread going so I did the compression test with several different exhaust configurations. The snap varied by 10 points. W Mufflers it was 100 and without but rear mounted x pipe was 110. Don't know what to make of that yet.


    I was one of those callers a few months ago, I really couldn't answer any questions until I had it running. Now that its running I have something to go off of.
     
  4. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
    Member

    Spark KV or kilivolts is pretty tough to measure and does require a scope for secondary ignition. We use a four chanell lab scope ( A Pico) and they are fairly expensive.
    The coil test is pretty easy just measure with a ohm meter the resistance across the primary (usuall .5 to 4 ohms always less than 5 ohms)
    and the secondary from the center tower to one of the two primary terminals ( should read in thousands like 7-8000 ohms etc.
    If both measurements are within spec the coil will more than likely work....
     
  5. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
    Member

    Really theres lots to gain from the MSD box we use a ton of the new CDI box ( cheapest box they make) to give the ignition contacts a very long life. It will improve the reliabiltiy of the entire sytem.
    I have nothing against the use of the red boxes , however many times its money spent for something not really needed when the car could benifit more with another part here and there. I see very unsafe tires with a MSD box on the firewall...

    The mallory brass condesnors are usually ok , just tested one this morning that test perfect. We just polished it , shot it with clean paint and its running right now....
     
  6. Dwell is the amount of time, measured in degrees of rotation, that the points are closed allowing current to pass to the coil's primary windings. An 8 lobe cam needs to open the points every 45 degrees to collapse the primary windings and produce secondary voltage to the spark plugs. But a 4 lobe cam only has to do this "switching" every 90 degrees and the dwell time can be extended, with the additional rotation available, providing additional coil saturation.

    Look at the tuneup specs for older engines. Eight cylinders typically called for something like 28 to 32 degrees of dwell. Six cylinders got maybe 4 to 6 additional degrees and four cylinders even tend to get a few more.

    Also with the 4 lobe cam the rate of opening for the points can be slower and gentler. At higher RPM this can reduce the chance of point float and bouncing causing erratic ignition timing. Seeing this happen with a distrIbutor spinning on a distributor machine is a real eye opener. :eek:
     
    Last edited: Nov 5, 2012
  7. revkev6
    Joined: Jun 13, 2006
    Posts: 3,351

    revkev6
    Member
    from ma


    ok, give me an inch Im taking a foot!

    any 7mm black wires you know of that would work with both the flat top cap and the MSD box??

    is there a way to test the condenser separately from the dizzy with a meter??
     
  8. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
    Member

    oK guys i have a neat video showing a mallory on the tester running etc with a good spark advance curve.
    This is in a .mov file . I have uploaded these in the past any ideas on why i cant get this to work today ????
    Or just a lesson on how to do this....??????
     
  9. revkev6
    Joined: Jun 13, 2006
    Posts: 3,351

    revkev6
    Member
    from ma

    Bubba, post it up on youtube then paste the link into your post! if you don't have a youtube account email it to me revkev6*at*gmail.com

    edit* my gmail attachment limit is 25mb...
     
    Last edited: Nov 2, 2012
  10. sololobo
    Joined: Aug 23, 2006
    Posts: 8,176

    sololobo
    Member

    Classic cool information guys, makes me feel very good about my new engine I am installing soon. Thanx! ~sololobo~
     
  11. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,962

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Subscribed...........and Thanks, Bubba, for taking the time to post this info.

    Ray
     
  12. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
    Member

  13. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
    Member

    Beats me on my problem with the video today.
    This was a Mallory we just rebuilt for a flathead ford.
    First of video i just took it to 8,000 rpm for a little break in.
    Then observe when it slows to idle speed the ring shows zero advance . Notice when the rpm increases so does the advance , Thats the way they all should work.
    The Ford factory spec is 11 1/2 degrees ( 23 engine) at 3400 rpm etc . The early Ford was vacuum and almost never supplied this number. The Mallory is all mechanical advance and is the most adjustable unit out there...
    This one supplys 24 degrees ( engine) at 3400 rpm and is pretty smooth for this engine...
    Very seldom do we ever need "more" advance we just need it to come in sooner to match the vehilce , ie : gear ratio , tire height and rpm band.....
     
  14. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
    Member


    Moroso makes some 7mm wires with a carbon core in black...
     
  15. Thanks for putting the time into this !!
    This is a post of yours from another thread.
    I've read it at least 10 times and I get lost right before you get to the part about 10 volts drop.
    Any chance you could clear that up or when and where exactly should I be getting 2 volts and what's the other resistor ohms reading supposed to be?
    Thanks.


     
  16. fastlane666
    Joined: Sep 10, 2012
    Posts: 45

    fastlane666
    Member

    less is more tune in tokyo.
     
  17. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,980

    s55mercury66
    Member
    from SW Wyoming

    Also I am wondering if it is really worthwhile to bypass the ballast resistor when starting. What 31Vicky posted above has also given me a new understanding of why my old Sportster ate points on a regular basis. Thanks for the info.
     
  18. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
    Member


    It was too big but thanks...

    Bubba
     
  19. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
    Member

    Not a problem thats the purpose of this thread , to clear up some wives tales.;)

    You would have in that example 2 volts at the negative terminal of the ignition coil. The final drop isnt a direct resistor but a finely stranded wire allowing only xxx amounts of voltage to travel thru it. Kinda a variable resistor or sorts.
     
  20. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
    Member


    The resistor bypass was designed for slow, cold weather starting issues. A cold engine with thick dirty oil, a worn starter and a weak ignition coil needed every bit of help it could get.
    Its hard to imagine how bad some cars can get with no maintence!!!!!
     
  21. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
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    Ok , looks like we are covering some ground here . Thats good !!!
    Lets talk some more in regards to this ignition voltage.

    MISFIRE: A secondary ignition "misfire" occurs when the required voltage exceeds the voltage available.

    In our example that would be over 30,000 volts !!!!
    Its actually pretty hard to exceed the 30,000 volts but it happens.

    I just looked at a flathead in a 50s car that was hard to start. Every part was new and the carb had been apart many times trying to fix the hard start .
    A scope check showed 25,000 volts when cranking at the coil wire !!!
    A visual inspaection showed the brass end of the coil wire had been pulled loose and the spark was jumping about 1/2 - 3/4 inch !!!! Had one hell of a coil on it to make that happen!!!!!!!:eek:
    A new coil wire was made up and the car now starts right up!!
     
  22. revkev6
    Joined: Jun 13, 2006
    Posts: 3,351

    revkev6
    Member
    from ma

    bubba I've got a cheapo craftsman pocket digital multimeter, can I use that to check the condensor?? I've read about using an analog meter to measure the resistance. from what I read it seems it should start right at zero and bump up to infinity?? I don't think this test works with my digital meter. I measure it one way and get a fairly stable resistance then I measure it the other it seems that it keeps charging and discharging as the resistance cycles up then drops. I might just throw it on my flathead to see if it works??
     
  23. Sheep Dip
    Joined: Dec 29, 2010
    Posts: 1,572

    Sheep Dip
    Member
    from Central Ca

    I read the same thing basically he said a spark was a spark as long as it was introduced at the right time.
     
  24. Budro35
    Joined: Dec 22, 2007
    Posts: 114

    Budro35
    Member

    Subscribed - More Bubba!! More!! :D
     
  25. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
    Member

    Could be very true!!!

    In the 12 volt world we started with charging voltages as low as 12.2 volts and up to 16 volts ( early alt Caddy).
    Could very well be that your pontiac was a 13.6 (etc) car and the 14 plus causes some arc over in the distributor..
    Whats the year , make and model and i will pull the spec sheet for your car to see waht the regulator setting was ???? Will make a good example for this discussion...
     
  26. mynode
    Joined: Sep 22, 2012
    Posts: 25

    mynode
    Member

    You're not going to get 30,000V at high rpm because the dwell time is too short to saturate the coil. I recall reading somewhere that the red line of the Shelby 289 motors was limited by the ignition system. It wouldn't produce enough spark energy to ignite the mixture and the engine would start to misfire.

    There are two ways around this. One is to use multiple coils so that you can have dwell time for different coils overlapping. The other is to boost the primary voltage up which will reduce the time to saturate the coil. MSD and the various CDI systems take the latter approach. If you boost the voltage up high enough, you can saturate the coil fast enough to trigger a spark several times in a single ignition cycle - hence the "MS" in MSD.
     
  27. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,884

    dirty old man
    ALLIANCE MEMBER

    Bubba, you've touched on spark advance in this thread already, but I'd like to read your thoughts on vacuum advance, ported or direct manifold?
    Different articles say opposites on this.
    I understand that some cars came with a temp controlled switch that changed from ported to manifold after warm up?
     
  28. RodStRace
    Joined: Dec 7, 2007
    Posts: 2,527

    RodStRace
    Member

    Bubba, great stuff.
    I want to mention something you said earlier, just to clarify it.
    Many rodders, especially newbies equate the word 'emissions' with smog equipment and have an intense dislike for anything that has to do with it. When you used the term emissions you were referring to radio frequency emissions or 'noise'. The solid core spark plug wires and non-resistor spark plugs created a lot of this. Suppression wires and resistor plugs helped stop this. Another item used to combat this is the Corvette shields many have seen.
    Since the hood and firewall were not made of metal, the RF could interfere with radio reception. They installed these shields to prevent this. If you are running hoodless, they can help radio reception IF you are still listening to AM!
    [​IMG]
     
  29. RodStRace
    Joined: Dec 7, 2007
    Posts: 2,527

    RodStRace
    Member

    Don't forget that a CD or other electronic ignition also helps increase dwell time over a point type ignition due to the physical limitations of the points.
    A point set must have an opening and closing ramp that will operate over a wide RPM range without bounce or changing the opening point. They must also not have so strong a spring that the cam or rubbing block wears quickly. It also must physically open enough to cause the circuit to open, which is why most point gaps are similar, even with different numbers of cylinders. Due to all these physical limitations, points can only provide so much dwell time. That's why dual points were used. They allowed both sets to open and close according to the physical limitations, but the two sets were offset slightly so that both needed to be open to cause the circuit to open and the field to collapse. This allowed the dwell to be longer than a single set could provide. An EI system does away with this, simply triggering from a signal for the transistors inside the box to open the circuit and collapse the field.
     
  30. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,385

    GMC BUBBA
    Member

    I plan on working up to the late model and aftermarket ignition systems, but we need to clarify a couple issues being as we brought them up.

    MSD multi spark (like most multi spark) goes away at approx 1800-2000 rpm and becomes a single spark. The only full function multi spark on the market today is the newest Pertronixs with multi spark all thru the rpm bands . We have tested this with a lab scope at 9000 rpm and above. Its kinda a moot point as the time span is so short at 9000 rpm only a lab scope stretched out shows a multi spark...
    Multi spark was created by Ford in a effort to get their cars thru emission testing with a very lean ( almost unfireable) air fuel mixture.

    As far as the 30,000 volt numbers those are for driving down the road under load NOT at high rpm. Voltage requirement at high rpm becomes a factor of how much time do we have to ramp and fire ( like you quoted above) the coil.
    At wide open throttle the air fuel mixture must be very rich and the required ignition output becomes a factor of time and load.

    I believe the output of the shelby ford engines ws a limit of camshaft and valve train and over all engine design NOT ignition...:):eek:
     

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