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Ignition Upgrades

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 76 jimmy Az, Apr 27, 2000.

  1. 76 jimmy Az

    76 jimmy Az Registered Member

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    Hey any one with a jimmy around my year that out in an ignition upgrade from jacobs or msd. And if you did, did it improve the throttle response and gas mileage like it is claimed to do. Someone told me that this upgrades dont do well in order trucks like mine thanx
     
  2. jmpd

    jmpd 1/2 ton status

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    Check a few pages back. there were a lot of posts on the subject. try doing a search

    Good luck
    Michael
     
  3. SnakeEyes

    SnakeEyes Registered Member

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    I didn’t check the other thread but I can tell you for a fact that adding the MSD-6 with the HEI module upgrade from Summit or Jegs will improve ANY engines ability to fire, thus improving mileage and performance especially in the low RPM range that most 4 wheelers are useing If you have the cash, do it!! I beleive that Jacobs is over priced but they stil get to the same place!
     
  4. Depdog

    Depdog 1/2 ton status Author

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    Never had any experience with Jacobs, have always seen way more negative about them than positive though. I have had an MSD 6AL, it gave my little Ranger better throttle response and smoother idle.

    I have a 77 with the vacume advance HEI. I just installed a CRANE HI-6 Ignition and in the cap coil. WOW, it made a very big differece in idle quality and low end power. It used to buck and give me fits if I tried to do very low r.p.m.s in a higher gear, not any more, it just pulls and drives smoother now. Its not going to give you a tire spinning axle snapping boost, if that is what you are after better look at nitrous. It will give you a smoother idle, better throttle response and if you get the timing retard control like I did, it will let you retard or advance your timing, or both, depending on how you set it up. That helps when you are pulling a heavy load or you get some bad gas, you can get rid of the knock.

    Damn Knew I forgot something, the CRANE has built in rev controller, it has 2 rotary switches that you can set the rev limit in 100 r.p.m. incriments so you dont have to buy the right r.p.m. module or get one of the soft touch rev controllers. On the Vacume advance H.E.I. it also removes the stock ignition module and hooks to the stock magnetic pick up and the computer does all the work.

    Depdog

    <font color=blue>"Lead, Follow, or BECOME the Trail"</font color=blue>
     
  5. Brad

    Brad Registered Member

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    I have an 84 Jimmy that is totally stock (38,000 miles on 305 5.0 L). Two weeks ago I added a MSD 6A ignition, MSD super coil, Accel dist/rotor, Jacobs wires, and Bosch platinum +4 plugs. The Jimmy already started well, so I didn't notice much improvement there, but I did notice a BIG difference in the "go" from a standstill. No more hesitation, more power...would definately do it again.
    By the way, I wired the MSD box directly through the pick up coil wires instead of the factory ignition module.
     
  6. SnakeEyes

    SnakeEyes Registered Member

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    DepDog:
    Is the Crane unit a "Multiple Spark Discharge " unit, that is does it fire across 20 or 30 degrees of crank rotation below 3000RPM like the MSD or does it not? Never been able to get a clear answer on this although I havent called Crane
     
  7. NYC K5

    NYC K5 1/2 ton status

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    im running the jacobs omni magnum and have notice a significant improvement in gas milage idle quality ease of starting and power
     
  8. Depdog

    Depdog 1/2 ton status Author

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    Its multiple spark discharge below 3k rpm's up to 12 sparks. After 3k the number of sparks fired is adjusted to maintain a total spark duration of 20 degrees of crankshaft rotation...

    Thats straight from the book, well, the figures anyway, I took out all the bull crap words in between.

    Depdog

    <font color=blue>"Lead, Follow, or BECOME the Trail"</font color=blue>
     
  9. SVBlazer

    SVBlazer 1/2 ton status

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    I too have the Jacobs box and have had simular positive results. Mileage improved, hesitation stopped, seat-of-the-pants-power seemed to improve too. I use Autolite 24 plugs (about .99 ea) and have to replace them every spring. The gap is huge .060! I'm running a 85 with a 383. Hope this helps.
     
  10. 76 jimmy Az

    76 jimmy Az Registered Member

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    hey guys thanx for the help especially on buying jacobs or msd. This is a great message board
     
  11. Eagle86K5

    Eagle86K5 1/2 ton status

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    Hey Depdog...

    would you advise the same setup for a stock 86 305?

    <font color=green>[​IMG]Eagle86K5[​IMG]
     
  12. 73/75 k5

    73/75 k5 Registered Member

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    I used to have the mileage master setup by jacobs. It came complete with coil,wires, and box with all waterproof connectors with no splicing into existing harness.Instructions were very simple also. BUT ever since I installed it, my truck would hesitate in the mid RPM range(1500-3500). I adjusted my carb, tried different plugs, changed timing with no solution but possibly a bad box. Luckily I was working at a speed shop at the time so I was able to swap the box for another one. Still did the same thing. So I opted for the MSD-6al. Best thing I ever did. I think it responded way better and no more hesitation. I then also put on the MSD wires(supposidly the least ohm per foot wire).I must say though I am still using the coil by jacobs, no problem there.Hope this helps. Oh ya and the jacobs has an anti theft toggle that you can install. Pretty cool option, you just have to remember that you have it turned on or else you'll drive for about 20 seconds and your truck will die and you won't be able to restart untill you reset the toggle.
     
  13. Depdog

    Depdog 1/2 ton status Author

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    Yes, I dont know if you want the timing control or not, its cheaper without it. I have been very pleased with this one and like it more than the m.s.d. I had in the ranger.

    Depdog

    <font color=blue>"Lead, Follow, or BECOME the Trail"</font color=blue>
     
  14. Eagle86K5

    Eagle86K5 1/2 ton status

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    What do you mean about timimg control....?
    Is it like the drag folks use ...got a meter and knobs so you can adjust the timing from inside?

    <font color=green>[​IMG]Eagle86K5[​IMG]
     
  15. Depdog

    Depdog 1/2 ton status Author

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    It has a knob that shows from 0 to 20 degrees, it is for timing retard, you can put it in the middle then set your timing where it is supposed to be and have 10 degrees either way. It has an led on it to show its working.

    Depdog

    <font color=blue>"Lead, Follow, or BECOME the Trail"</font color=blue>
     
  16. NYC K5

    NYC K5 1/2 ton status

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    73/75 k5 i think me and you are the only two people on this site who like the jacobs. the only people i ever heard that have had problems with them had the racing box. and thats only one guy. i havent pulled my plugs in a while, after how many miles do you change yours?
     
  17. Eagle86K5

    Eagle86K5 1/2 ton status

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    So Dep...

    Just what is the model number, part numbers, names of just the stuff I need, remember ..presently my 86 305 is completely stock...thanks man. And by the way....my best friends are LEO's....

    <font color=green>[​IMG]Eagle86K5[​IMG]
     

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