MSD Idle Question

Discussion in 'Trucks and Trailers' started by 85w/350, Apr 1, 2001.

  1. 85w/350

    85w/350 LawnSite Member
    Messages: 244

    I just spent this weekend installing an MSD box on my 85 GMC 350c.i. I replaced the coil, cap and rotor and added the MSD all in one day. It feels like with the MSD it idles a little faster and it vibrates a little more. I can hear a couple hard bumps every now and then in my exhaust. I can definately see a little bit of performance increase but this faster sounding idle bothers me a little bit. I didnt change the plugs and they havent been changed in awhile do you think they could be my problem or is this just a normal thing after installing the MSD box? Its a 6A box so supposedly it puts out 6 sparks for every 1 I used to get.

    BUSHMASTER LawnSite Senior Member
    Messages: 519

    if i remeber right msd made a special box for use with hei you might check into this also the standard hei wires are definilty too wimpy to handle the extra fire ,which would also cause a skip and check the heat range of your spark plugs i think thier is a change needed their,and if you index your plugs your get even more puts out more fire which comes from more heat and spikes in the spark, weather its a 5a, 6a ,6al, etc etc the same principal applies.

    [Edited by BUSHMASTER on 04-01-2001 at 11:22 PM]
  3. 85w/350

    85w/350 LawnSite Member
    Messages: 244

    Sounds right i think i have heard that somewheres before I asked a friend who is also a mechanic to listen to it and he says it sounds about right its mostly because each cylinder is getting fully combusted which could be causing it to turn over faster but its consuming less fuel...I'll be able to check it next trip I take...I can't wait to see what new plugs and wires do :-D

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