HEI Ignition

Discussion in 'Trucks and Trailers' started by 84'GMC4x4, Feb 12, 2001.

  1. 84'GMC4x4

    84'GMC4x4 LawnSite Member
    from MA
    Messages: 84

    anyone know the quickest way i can tell if i have HEI? my truck is an 84 GMC w/350, i noticed the other day that my cap & rotor are badly in need of replacement, i would like to upgrade to HEI if it's not too much $/hassle.
    any advice/comments welcome
  2. wyldman

    wyldman LawnSite Member
    Messages: 182

    Your 84 should have factory HEI ign.One quick way to tell is do you have a separate coil ? If not you have an HEI.The coil is in the cap.
  3. John DiMartino

    John DiMartino LawnSite Silver Member
    Messages: 2,555

    You already have HEI,Gm has used HEI since 1975,if the cap and rotor were gone,consider a new coil too,while your in there.
  4. 84'GMC4x4

    84'GMC4x4 LawnSite Member
    from MA
    Messages: 84

    yes, the coil is in the cap,so i guess i have HEI. thanks for the replies guys.

    John, i will be replacing the coil too, thanks for the help.


    UNCLE BOB LawnSite Member
    Messages: 99

    I would recomend buying a new(Control Module),just in case.I had a blazer,in which the control mod. blew TWICE, both times on I 95 and when it goes ,your truck is DEAD. I pulled my distributor,found a chiped gear. New dist."cheap" module's $175.00 x 3= OUCH. I never left home with out one.
  6. mike reeh

    mike reeh LawnSite Member
    Messages: 229

    uncle bob what exactly does the electronics dying have to do with chipping a gear? and what gear chipped? the dist. drive gear??


    UNCLE BOB LawnSite Member
    Messages: 99

    Yes the dist. gear on bottom of shaft,When it hit the bad spot it increased speed from missing the chipped spot,inturn increasing the juice and burning the module until it could'nt take anymore and blew.which was about every week and a half. Twice.Until my buddy said "let's change the dist." And there it was.
  8. Alan

    Alan Member
    Messages: 1,185

    I'm a little dense, how did having a bad tooth on the drive end make the distributor "increse speed"? Since on one tooth (on a helical cut gear) is ever carrying the whole load, how did it affect anythign unless it was totally missing? Even then I can't see how it affected voltage through the module. If it was missing so much gear that it was affecting the electronics, how did it manage not to jump timing by one tooth for every rotation of the distributor? There's something funny here and I suspect there was something else wrong with your distributor.

    UNCLE BOB LawnSite Member
    Messages: 99

    I dont know,but that is what my buddy said.It was skipping,wobbling or something.All i rember is the gear on bottom of dist. was damaged,we replaced the dist. and never had another problem! Sorry If my description of the problem was off.
  10. RTallday

    RTallday LawnSite Member
    Messages: 214

    I believe that HEI was an option for a while, because i had a '76 C-10 and it didnt have an HEI dist, it had the regular cap and coil. My 79 K-20 has HEI and it is listed on the option sheet, and it was origionally made by ACCEL. There is also a sticker on the fire wall right above the distributer. Just thought i would share that.


Share This Page