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Jacobs Ignition for TBI ??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Range Boy T, May 2, 2002.

  1. Range Boy T

    Range Boy T Registered Member

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    I have an 87 Chev, 350 TBI, Th-400/208. I have a Jacobs Ignition System for it, but i am not sure on what
    exactly the pro's and con's are. I read on here about what a lot of you were saying about it, but nothing was mentioned about the TBI system, i think. So my ? is, what ARE the pro's and con's in installing the
    ignition system?? The system works, and it cost me nothing, so anyway. Thanks
     
  2. NorthernRedNeck

    NorthernRedNeck Registered Member

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    No benefits...better sell it to me lol Hope sumone can b more helpful than myself cause I am curious too
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    If its anything similar to MSD-6A, I'm gonna be one of the few people to say only bad things. You don't need it (stock spark is adequate beyond what you will turn the motor at unless racing, and even then...) it doesn't increase power (show me non-ignition company dyno tests that show it does, vs a brand new HEI setup) and it is yet another wiring hassle added into the ignition system, that should something fail, makes it even more difficult to diagnose.

    People mention easier starting or smoother idle, and not having run one, I can't comment on that. If that negates the above statements I made for you, then go for it.

    http://yeagerd.home.mindspring.com/ignitiontest.html

    Wish I knew for certain that the baseline was just a stock dist. with a better coil in that test, more useable power made by it than any of the others tested! The test is flawed IMO because they did NOT test it against a "stock" HEI system as far as I can tell...but looking at those numbers, they used old plugs and wires for baseline, new for all the other "boxes" and the "stock style" came out ahead at all but the highest RPM's.

    No way in heck I'd spend anywhere near that kind of money on something that can't even make more power on better plugs and wires...I'll put up with "crappy" idle if it means more power all the way up to 4200RPM, and getting the kinda mileage I am.

    BTW, for anyone curious, I'm getting same mileage with plugs gapped at .050 as I was at .035/.045, on teh stock HEI, with no loss or gain of idle quality.
     
  4. jimmy88

    jimmy88 1/2 ton status

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    Don't know which Jacobs you got, I've had the Omni pack on the 88 burb wTBI since 95. It runs slightly better, but the improvement was NOT worth the cost to buy it. Guess the stock TBI ign was pretty good from the factory. I left the stock coil in place as a back up system. I keep the stock coil wire in the glove box and can switch from the jacobs back to stock by changing the two connectors and the coil wire. If you got it already I'd say put it on.
     
  5. Range Boy T

    Range Boy T Registered Member

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    Thanks, i think i might try that. If ya don't mind could ya send me a rough diagram on how you did that. I wanted to do something like keep the stock coil, and use the Ign Sys, but i was not sure on how to rig it up, electronics not realy my thing. Thanks again.

    Tim
    87 Chev Silverado 350/TBI TH400/208 dana44 14 bolt/w detroit 35" swampers
     
  6. CaptCrunch

    CaptCrunch 1/2 ton status

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    First off for like the fourth time this week... jacobs is junk. Check the past post using the search feature. What Dorian says is true. Your stock ignition system is adaquate up to 4500 or so rpm no problem, although a stronger coil sometimes will make a bit more power if you open up your plug gaps a bit. But overall really depends on your combo.

    I personally have the MSD offroad box and love it cause sometimes in the mud I wind the motor up a bit to make up for my smaller 35" tires. I actually noticed a bit better gas milage as well, but hard to say with new plugs and stuff done at the same time. Personally I would save you money and just get a go set of msd or taylor plug wires, open the gap up on your plugs, and get a higher power coil like a MSD
     
  7. jimmy88

    jimmy88 1/2 ton status

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    If he has it already, why not try it as long as it won't hurt anything else? I agree its not worth buying though.

    Tim, the omni pack is coil with the electronics built in the same housing (probably just a plain coil priced high). If you got the seperate control like the energy pack and don't have the original instructions to install it or the stock type wire connectors its not worth your time hacking up the stock wiring, just bag the whole idea.
     
  8. sosamantx

    sosamantx 1/2 ton status

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    i've personally heard nothing but bad things about the jacobs ignition system!! not only on this board, but in r/l, i however am not sure about the TBI version. i will say that i've had my msd 6a (on my nova), since 87, and have only had problems with it once, never figured it out (in the 1-2 days it wouldn't start), and it has never done it again. i had started to trouble shoot it, and maybe i just had a loose connection or something? anyway, once i get my tranny working/fixed, i'll be getting a msd unit for my blazer. it did make for easier starts, and did slightly better on gas mileage. so to sum it up, i'd say if you got it for free, traded for it, or whatever, i'd still be leary about the unit. the only thing i've ever had of jacob's are the plug wires (which were good at the time), but i'm being told they are junk compared to what is out there now.
     
  9. CaptCrunch

    CaptCrunch 1/2 ton status

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    Main reason is reliability. I know two people with Jacobs stuff and they had problems that left them on the side of the road, but if you don't have to hack up the stock wiring (which I assume you will at the coil connection to connect the box up). I like the fact that msd has harnesses so if it does fail I can pull off the harness and reconnect the stock wiring and bickity bam... she's roaring on home. MSD has had issues with water and weather in the past, but my offroad box has faired excellent thus.
     
  10. SVBlazer

    SVBlazer 1/2 ton status

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    I'd like to be the different voice here. I have a 383 with all the bells. In round numbers 425 lbs/400hp. I've had a Jacobs omni mag and upgraded to the off road power pak. First, pre Jacobs mpg=10.2, post omni mag=11.8. I upgraded the 383 at the same time as the ignition system (LT1 heads, 280 cam and roller rockers). My current mpg=12.5. I'm running 3.73/33s. So, my experience is somewhat different. I'm happy with Jacobs. The tech support is first rate and the warrantee is great. I’ve burned a couple of plug wires and Jacobs has comp’d them out no problem in 48 hours or less.
     

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