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  •  » Spark plug wire separation?

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    8/31/2015 10:16 AM  #1

    DC
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    From: Marshall, MI
    Registered: 4/01/2013
    Posts: 1,251

    Spark plug wire separation?

    What does everyone think the minimum separation of wires should be in the spark plug wire loom? I am running a MSD 6AL with one of their Blaster HVC coils. Most wire separators give about 5/16 inch. Based on some funky things happening, I am thinking I may be getting some cross talk. I tried new cap and rotor and then noticed some of the wires a little close to each other.

     

    8/31/2015 12:23 PM  #2

    Rudi
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    From: Stuck in the 50's Welland Ca
    Registered: 4/01/2013
    Posts: 3,992

    Re: Spark plug wire separation?

    I have 1/16" between some wires and no "cross talk"
     Crane High six ignition with high output coil.
     How old are the wires?  Are they yellow?

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    9/01/2015 5:58 PM  #3

    TKOPerformance
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    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,599

    Re: Spark plug wire separation?

    If you're running a good set of performance wires I don't think its much of an issue.  Its always advisable to keep the wires for cylinders that fire sequentially away from each other, but other than that I've never had cross fire with good wires.

    Other than that, be sure to change the wires every couple of years.  The insulation breaks down from age, not use, and that could cause cross fire or other issues. 

     

    9/01/2015 7:18 PM  #4

    DC
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    From: Marshall, MI
    Registered: 4/01/2013
    Posts: 1,251

    Re: Spark plug wire separation?

    I am getting a little wiggle in the tach and I can feel it in the pull of the motor. Just happens once in a while and seems like the motor wants to pull better but is getting confused. I will put more separators on the wires and try a track day to see if that is it. I will also take complete new ignition parts to swap if that is not the problem. My new set of parts is the newer MSD 6 unit that may be the fix. Seems like they have upgraded for higher RPMs which I am running now with the newer motor.

       •Thread Starter
     

    9/02/2015 10:58 AM  #5

    BobN
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    Registered: 4/03/2013
    Posts: 158

    Re: Spark plug wire separation?

    For the last 20 years, I have always made my own seperators out of zip ties. I have never had issues, and the best part is if they get messed up or need to be replaced, the price is right!

    I, of course, do not have any pictures of my loom seperators, but there is a video on youtube on how to make them:
    https://www.youtube.com/watch?v=xWO1Oes7oJw

    I of course use black zipties for my black ingition wires, but you could use white or red or yellow if you so desired.
    BobN

    Last edited by BobN (9/02/2015 10:59 AM)

     

    9/02/2015 11:10 AM  #6

    GPatrick
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    Re: Spark plug wire separation?

    I think the bigger issue is the actual routing of the wires.  Depending on firing order, the 6-5 firing on some small blocks and the 7-8 firing of other small blocks and FE's for example are particulary prone cross-firing.  These wires in particular should be routed separately.  For example, keep 7 and 8 at opposite sides of a wire loom and then route 7 around the front of the engine and 8 directly towards the back.  Cross-firing can be inductive in nature - not just an arc between wires.  If you were to run the two wires side by side there is a chance for inductive cross-firing even when using very good wires.  I know the FE's are particulary sensitive to cross-fire and the issue is not necessarily miss-firing but a premature firing of number 8 cylinder that can put a lot of stress on the crank.  If given the choice of cheap wires or the advertised very best I would still route the sequential firing cylinder wires as far apart as possible.

    Not sure it was mentioned but rotor cap condition - carbon tracking or tracing depending the article you read - can also lead to cross-firing or mis-firing.  Additionally, as discussed to excess a few months ago, rotor phasing can also lead to a condition of mis-firing or cross-firing especially when the distributor is at maximum mechanical advance.

     

    9/02/2015 1:04 PM  #7

    MS
    Forum Originator

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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,347

    Re: Spark plug wire separation?

    Yep to what Gary said.  Ford always crossed the 7 & 8 wires on 351 engines to avoid the inductive firing of consecutive cylinders.  If a different cylinder inductive fires from having the wires parallel, it doesn't matter due to the timing of the compression strokes.  If it fires a plug on the  exhaust stroke, no problem.  But if it fires it as the piston is at the bottom right after inhaling a charge of gas on the intake stroke, that particular piston then goes to TDC with the charge already having been ignited, causing a misfire.

    Crossing the wires will cancel out any possibility of an inductively induced firing.

    All that said, I sure like mine parallel and in ship shape order !!!  And I like that zip-tie idea.  Clean and effective and they will never pop loose.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    9/03/2015 7:28 AM  #8

    DC
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    From: Marshall, MI
    Registered: 4/01/2013
    Posts: 1,251

    Re: Spark plug wire separation?

    Thanks for all the good info. I will follow each wire and make sure there are no parallel runs. I am running the 13726548 firing order and will make sure no adjacent ones are near each other. I may have to make a couple of new wires to route a little different (messy'er).

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