1. brotherGood

    brotherGood Well-Known Member

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    Alright, ever since I swapped engines, I've had a slight miss at high rpm. While the engine isnt stock, I wouldnt have initially thought it was enough to require a bigger coil. Currently, im running a 318 LA block, with magnum heads that have had a valve job done. Im using shim gaskets, have a summit 6900 cam and summit 600 carb.

    It has a new distributor with the rebuild, and we added a new pcm, cap/rotor/wires as well. I've been reading the factory coil may not put out what is required when you start really modifying it, and I wasnt sure if that's my issue.

    Thanks
     
  2. Aspen500

    Aspen500 Well-Known Member

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    A "hotter" coil wouldn't hurt anything but maybe simply a new coil? They can deteriorate enough to not put out the voltage they once did. Not sure if some of the windings short together and essentially reduce the number of windings which causes lower voltage output or what. Happens with distributorless ignitions as well as coil on plug so why not single coil systems, too?

    It is possible the high speed misfire is caused by the ECU also, especially if it says "Made in China" on it somewhere.
     
  3. brotherGood

    brotherGood Well-Known Member

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    Coil is about 5 years old..been used for maybe 2..lol

    (Potential stupid question...difference between PCM and ECU on these things?)

    The autozone version of an orange box..thats what is on it...its chrome
     
  4. Aspen500

    Aspen500 Well-Known Member

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    A PCM is a "Powertrain Control Module" and is a computer processor that may also control the trans. ECU is Electronic Control Unit which is more like the ignition module. Of course a PCM is also called an ECM (Electronic Control Module) by some manufacturers.

    Some driveabilty problems you end up substituting a known good part and seeing if it's fixed. That's actually a step in a lot of factory diagnostic procedures. After eliminating faults you can check (wiring, etc) the manual will say "Substitute known good part" Sometimes easier said than done and known good doesn't necessarily mean new..............trust me!:confused:
     
  5. brotherGood

    brotherGood Well-Known Member

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    Im not sure where the ecu was made..but wouldn't be surprised if it was Chinese. I know we could see a great improvement in spark when we put that box on. I may pick up a different coil just to try that out. At the very least, it'll ensure everything is new since the engine swap.
     
  6. wvdodgemirada

    wvdodgemirada Well-Known Member

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    Have you checked total timing? Cause last year mine developed a miss at higher rpms, and after ruling this and that out we finally checked the timing and I had lost 12 degrees. The distributor was maybe 5 years old, and had been recurved maybe a year before this happened. As with everything, it could be a lot of things causing your issue. lol
     
  7. brotherGood

    brotherGood Well-Known Member

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    Once I get the fuel lines back together, im gonna throw plugs in it and check total timing. Whenever I get someone to help, the car is down for one reason or another. I had planned on verifying that anyway, but im still sketchy on how to not only check it, but adjust it.
     
  8. BudW

    BudW Moderator Staff Member

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    You can get an existing ignition coil to run hotter, by lowering the resistance in the ballast resistor (which means finding a different ballast with resistance you are looking for). Doing so, can, and will, make your existing ignition coil fail faster.

    If you are only going to use it for short periods of time (drag racing, etc), you could bypass the ballast resistor altogether - but you will only be able to do this a short amount of time (and you better have a spare ignition coil in the trunk).

    I know on my ‘87 Daytona Shelby turbo, I could disconnect the vacuum hose going to the ECM (Engine Computer) and it would run much better (it was faking the computer and turbo wastegate) - but it was also a very good way to blow things up. I, um, only did that for a couple of impromptu street events and testing purposes. Note: this does not work with Lean Burn.