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HEI with vacuum and ECM???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Rich84, Sep 2, 2000.

  1. Rich84

    Rich84 Registered Member

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    I have an 84 that originally had a 305, but now has the same year 350, that was installed before I bought it. None of the emissions stuff is there (o2, EGR, etc.). Vacuum is high and it runs good, but it goes through a tank of gas faster than an alcoholic goes through a bottle of tequila. I noticed the distributor has a 4-prong ECM connector and a vacuum diaphram, but I always thought it was supposed to be one or the other. If I disconnect the ECM, it won't start. If I disconnect the vacuum, it runs fine at all speeds. Haven't checked the mileage without the vacuum yet. Has anyone else seen anything like this? Does anyone with an 84 have either one or the other or both? Is it possible that I was getting too much advance? Timing is about 8 deg., don't know the advance curve yet.
     
  2. 4x4blazer

    4x4blazer 1/2 ton status

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    I have a 84 with a 350. Mine was origionally equiped with a 305,too. But that has nothing to do with how it is set up now, as they are both the same set up. My distributer is the same as you are explaining. My timing is at 8 deg. also, but I am not running a stock cam. If you have a stock 350 in your 84, I believe you should be at 4 deg. Set your timing with the vacuum disconnected from the distributer.
    Hope this helps.

    [​IMG]
     
  3. Thunder

    Thunder 3/4 ton status

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    If none of the emmision stuff is there, the ECM will be running on its default mode. One of the symptoms of this, is horrible gas milage.It is designed this way so the operator will get tired of feeding it gas and get it fixed. You need all the "stuff" (o2, egr and other sensors)To make it work right. To get better gas milage. Either put the emision parts back in or replace your ign and carb with aftermarket parts. If smog laws allow you to do so.

    [​IMG]
    Get Out and VOTE!
     
  4. Rich84

    Rich84 Registered Member

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    Thanks for the input. I haven't figured out what I'm going to do yet, but your replies help alot.
     

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