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HEI Question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 70jimmy, Aug 31, 2000.

  1. 70jimmy

    70jimmy 3/4 ton status Premium Member GMOTM Winner

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    I picked up a complete HEI for my 350, Used $35.00. My question is on the cap is a plug for wire from battery and tach. Power from battery? Does it come directly from battery or should it be from fuse box. Does it have to be hot all the time with a full 12 volts? ( I assume it does). I dont have tach yet so no problem there. Can you buy the plug at a parts store that fits the distributor cap? I am planning on changing the module, new plug wires, and plugs, then getting it running before I put on an accel super coil, or MSD coil on top. Any advice? I would rather stay away form seperate coil due to money issues. Thanks.
     
  2. '73 K5

    '73 K5 1/2 ton status

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    You can run the wire from the battery if you put a fuse inline with it, or you can get it from the fuse box. You could wire it with either a constant wire or a turnkey wire. When are you ever going to need it when the key is off? Thats why turnkey would be OK. You might be able to find a plug, or you could just use a regular female quick disconnect connector.

    '73 K5
    Chevy good...Ford bad
     
  3. Blazer1970

    Blazer1970 1/2 ton status

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    Running it from the battery would be OK, as long as you don't want to ever shut the truck off after you start it for the first time. You need a wire that is hot in "run" and "start" key positions only, not in accessory.

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  4. Emmettology 101

    Emmettology 101 3/4 ton status

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    There should be a wire coming off your harness you could tap into which needs to be and igniton control hot wire.

    As for the coils, I used an extrenal MSD for a while with the adapter and the MSD module with the MSD 6A box for a while, i liked it and never had probelms with it.

    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; http://emmett.coloradok5.com
     
  5. '73 K5

    '73 K5 1/2 ton status

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    Well ain't that some sh*t. I guess that would keep it running. Not a good way to help your gas mileage.

    '73 K5
    Chevy good...Ford bad
     
  6. talldogg

    talldogg 1/2 ton status

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    Blazer70, is right. You need to splice the 12v wire from the ignition switch. It's usually the red/dark pink wire. Find it, splice it and then run the wire through the firewall straight to the distributor. Last time I did this I placed a kill switch in between and I hid it really well under the dash. It worked great, it allowed power to get to the starter, but not the distributor. So if the switch was off and you turned the key, the engine would turn over but it would never fire up. That's better than generic kill switches that don't allow the starter to crank, letting the theif know that there's a kill switch on the car. This way a thief might think the car just won't start and they'll give up.
    Another plus is, since you have a 70, your sterring wheel doesn't lock (I think), so if you ever loose your keys you could run a wire straight to the battery and cross the starter solenoid over with a screw driver and the truck will start. To turn it off you just pull the wire.
     
  7. 70jimmy

    70jimmy 3/4 ton status Premium Member GMOTM Winner

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    Currently I have a points system, Does the current positive coil wire work off the ignition switch so that I could put a new end on it and use it? It goes to a 2 post box on the firewall and the other wire goes to the wiring harness on the firewall.
     
  8. talldogg

    talldogg 1/2 ton status

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    No, you need a constant 12v source. I don't know why that wire doesn't fit the bill, but every source I've seen always refers to drawing your power from the ignition wire. It's not that hard to find, on your 70, I imagin your ignition switch is on the dash not the column, right? If so, just get under there with a flash lite and you'll see it. It's pretty thick (I forgot the actual gauege of the wire) and it's recommended that the wire you use to go to the distributor should be at least the same gauge.
     
  9. Blazer1970

    Blazer1970 1/2 ton status

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    The existing hot wire to the coil uses a resistance wire from the connector on the firewall to the coil. The purpose of this wire is to drop the coil voltage to about 7 volts while the engine is running to keep the coil from overheating. This is not good for the HEI. What I did on my '70 Blazer was cut that wire off short at the firewall connector, and spliced (soldered) on a 12 gauge red wire to feed the bat terminal on the HEI.

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  10. talldogg

    talldogg 1/2 ton status

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    Blazer70 has it dead on the nail. His explanation for why not to use that wire is exactly what I remember now. His way of rigging it sounds easier, too!
     
  11. 87Blzr

    87Blzr 1/2 ton status

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    You guys with the old Blazers that originally had points should have a terminal in the middle of the fuse box labeled "IGN" with nothing going to it. Thats where you hook up the HEI lead to when you do the conversion. Directly from the HEI terminal on the distributor to the IGN terminal on the fuse box. If you go to a junk yard you can cut this wire out of almost and GM HEI car. Its a large diameter pink wire. Thats what I reccommed as it keeps your harness using the same wire and colors as factory setups so its looks more original and easier to troubleshoot using the correct wire diameter and color.

    87 K5 Siverado, 68 SS 396 Camaro
     
  12. blazer72

    blazer72 1/2 ton status

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    the ENG post on the fuse box on the 70 to 72 is only hot when the ken is in run not when its held to start! Ben there done that on mine! I'd go to the red with black stripe wire on the firewall cont. and splice in to just as was post above!

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  13. 87Blzr

    87Blzr 1/2 ton status

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    Maybe the terminals mean different things between the cars and trucks. I have done it this way on many cars including my Camaro with no problems. I just ran out to check my car to make sure. I figured it would be the same with the trucks but maybe not. It works on the old cars anyway. Sorry. If your gonna splice make sure its a decent wire that you splice into and use a decent wire to go to the distributor. It shouldn't be a regular small diameter wire.

    87 K5 Siverado, 68 SS 396 Camaro
     
  14. blazer72

    blazer72 1/2 ton status

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    I think the ENG term is hot in both run and start on cars. Theres a lot about the trucks fuse panel that is strange!! I finaly got feed up with the stock fuses and wireing and pulled them. I now am useing the Paneless stuff much better!

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  15. 70jimmy

    70jimmy 3/4 ton status Premium Member GMOTM Winner

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    Thanks for all the replies!!!!! Now its just to get my hands dirty and order some aftermarket toys. Pulling the dist with the motor in looks like a challenge with the dist close to the firewall. Thanks again
     
  16. Blazer1970

    Blazer1970 1/2 ton status

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    The distributor will come out, and the HEI will go in, as long as the cap is off. Check firewall clearance closely when you install the HEI.

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  17. blazer72

    blazer72 1/2 ton status

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    When I still had a dist it would hit the firewall at the very worst time and kill the cap!!

    I understand the jeep thing I drive a BLAZER!!

    Ken
     

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