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Thread: MSD Ignition

  1. #1
    EFI GearHead ! EagleMark's Avatar
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    This covers wiring of MSD 6a in all applications including installing it in a stock EFI system.
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    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  2. #2
    Super Moderator Six_Shooter's Avatar
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    The ignition module gets connected to the ECM, to both trigger the ECM and allow the ECM to control timing. The igniton control module also triggers the MSD box. Look at the points trigger setup using the white wire.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    Fuel Injected! JeepsAndGuns's Avatar
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    Ok now I'm getting confused. Are yall saying he can use the MSD box instead of the 8 pin HEI module (for the op, thats the ignition module used with a the 16197427 pcm we are talking about, and many others) Or are yall saying he can continue to use the MSD box WITH the 8 pin module?
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

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  4. #4
    Super Moderator Six_Shooter's Avatar
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    He can use the MSD box with the 8 pin module.
    The man who says something is impossible, is usually interrupted by the man doing it.

  5. #5
    EFI GearHead ! EagleMark's Avatar
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    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  6. #6
    Fuel Injected! JeepsAndGuns's Avatar
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    MSD Ignition

    Quote Originally Posted by Six_Shooter View Post
    He can use the MSD box with the 8 pin module.
    Not to highjack the thread. But next question is why would you want to install the msd box? Looks like its simply going inbetween the coil and the stock harness, so whats it really doing? Seems like simply adding un needed parts that could fail or make problems.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  7. #7
    EFI GearHead ! EagleMark's Avatar
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    Really it's not needed and wears out cap, rotor and spark plugs 3 times quicker.

    It fires spark three times at low RPM and one time longer at high RPM.

    Really helps in very rich old carbs with big cams. Helped to keep cars on carbs running WAY rich when Nitrous was not on and no way to add fuel like with EFI.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  8. #8
    Quote Originally Posted by JeepsAndGuns View Post
    Not to highjack the thread. But next question is why would you want to install the msd box? Looks like its simply going inbetween the coil and the stock harness, so whats it really doing? Seems like simply adding un needed parts that could fail or make problems.
    Why not? It gives you multiple sparks below 3,000 rpm. If it does fry and let the smoke out somehow, you simply unplug the connector harness and put the connectors back together with the OEM system. The make a plug n play harness for the GM dual connector coil.
    Familiar with 1227747 and 16197427 PCMs

  9. #9
    Super Moderator Six_Shooter's Avatar
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    The MSD provides a hotter spark than without. I would use an MSD box with a dizzy, due to all of the gaps that the spark has to juno on it's way to the plug. On DIS systems they don't provide as much of a gain or benefit.Caps and rotors don't wear out any quicker than without an MSD box.
    The man who says something is impossible, is usually interrupted by the man doing it.

  10. #10
    EFI GearHead ! EagleMark's Avatar
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    Quote Originally Posted by Six_Shooter View Post
    Caps and rotors don't wear out any quicker than without an MSD box.
    How can you say it won't wear out cap and rotor faster with hotter spark three times more often? It will also disenagrate a cheap quality cap rotor button leaving the spring dangleing in distributor! Using one on a large cap HEI distributor, carb 454 truck, we burned up three coils half way to Texas from Idaho, removed MSD box and drove the other half way to Texas and back home on one coil no failures. All personal experiances...

    If your going to use an MSD box then use MSD Cap, Rotor, Wires and Coil. This is the only way I never had a failure, but also was not a daily driver or did long highway trips.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  11. #11
    Super Moderator Six_Shooter's Avatar
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    I've installed many MSD boxes on cars using stock ignition components, I can't recall one premature failure of any part. I had a 6AL installed on my Sunbird and Skyhawk for about 2 years before I did an engine swap to an engine with DIS, never experienced any premature failure of ignition components.About your experiance, the first thing that comes to mind is poor grounding of the coil, the next thing is something wrong with the components used. Many people, myself included have used MSD boxes on in cap HEI coils without issue.
    The man who says something is impossible, is usually interrupted by the man doing it.

  12. #12
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    FWIW I've badged MSD as Must Soon Die. The race grade products are worth owning and there are systems built in the '70s and '80s that are still working fine today. But the consumer grade products are completely hit or miss, and when they're a miss they're a big miss. I've been left stranded in 3 of my own cars due to failures in an MSD ignition system over the years and I've diagnosed issues ranging from misfiring cylinders to poor quality REF signals to misinterpreted timing signals and random stalling back to consumer grade boxes.

    Large cap HEI in stock form will spark across a .100" plug gap with plenty of energy. Stock DIS systems in good shape can easily throw spark across .500" gaps. Unless you're running in an RPM range where the stock ignition system is having trouble or you have a specific set of conditions that are causing the stock system to perform insufficiently, I personally see no need to spend extra money on an MSD. If anything I'd get an improved aftermarket module and adjust the computer controlled dwell period in the stock calibration for slightly longer spark.

    More sparks in a given time frame can definitely cause more frequent parts failure. LT1 owners are probably familiar with GM's Optispark vent campaign in the early cars. Ozone created when sparks occur plus moisture in the cap would react and create nitric acid which would quickly degrade the rotor, cap, and even the distributor itself. The positive ventilation installed in the Opti ensured no buildup of ozone or nitric acid. I've used that same thinking plenty of times on standard distributors. Small cap HEI distributor rotors often get "stuck" to the shaft due to rust and I've seen the insides of the distributor full of corrosion from the terminals in the cap while the end of the rotor just sort of dissolves. In my '57 I cut the end off an old carburetor dashpot with a .020" orifice and installed it in the small cap dizzy. I connected the other end to ported vacuum so air would only draw through when the throttle is open. That was in '93. I have never changed the cap or rotor and they are still in great shape today. In our 5.7 Vortec vans we have problems with moisture buildup in the cap after a large rainstorm or on days with high relative humidity and large temperature swings. It's so bad it can actually cause a no start. In the 20 or so repeat offenders that I've installed positive ventilation the moisture problems are completely gone, and we've moved from changing the cap/rotor at 40-60k mile increments to changing it at 100k mile increments (or when the dang plastic body fails). When using a multiple spark or high voltage spark ignition in a street distributor I would definitely consider a similar modification. The more sparks occur, the more ozone is present, and the greater the potential for acid formation.


    Wasn't there an LT1 manifold swap somewhere in this thread?? :)
    EDIT: EagleMark Thread Split

  13. #13
    EFI GearHead ! EagleMark's Avatar
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    So that's what that green corroision is?

    FWIW the LT1 vent system is sold new still for like $56. It consists of vacuum line, an elbow to intake, a filter that looks like a one way valve (haven't tested if it is) on intake side to engine and I think... something else on intake to distributor... have to look later. I may do this upgrade on my Suburban as it was greenish inside last cap and rotor change about 4 years ago...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  14. #14
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    Quote Originally Posted by Six_Shooter View Post
    I had a 6AL installed on my Sunbird
    Funny you should mention that , I had a 6AL box on my daily driver Sunbird years ago also , simply because I could .....

    I will join the no problems club here , MSD ignition boxes , distributors , and electronics since I was old enough to buy them , I have never had a failure , or have experienced premature failure of any quality component.

    TOM

  15. #15
    Fuel Injected! PJG1173's Avatar
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    I run crane HI6 products in my two projects. haven't had any issues which I attribute to they are full digital unlike the MSD unit. I really didn't see any improvement by installing them though. I use them mainly for rev limiters since I would rather cut spark than fuel.
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