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  1. #1
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    Wasted spark or single spark

    Anyone know whether a chevy 350 short block utilises a wasted or single spark ignition. The information is needed to calibrate my tachometer.
    Thankyou

  2. #2
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    I assume you mean "small block" not "short block" as that's just half the engine! I am sure most use a single spark setup but to be honest thats entirely dependent on what the ignition system is, if you have an MSD or similar ignition system you may well be running a multi spark setup but I am pretty sure a wasted spark system is highly unlikely.

  3. #3
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    Depends on what your ignition system is (block type doesn’t help), dizzy/points/coil is single, electronic could be either, if so post the make up.

    Cheers
    Jim
    GD Mk3 Jag based
    Supercharged LS1
    GD J1M

  4. #4
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    Yes I meant small block , must have been a senior moment. I what I need to do is contact the engine supplier and get a definitive answer, to be honest its a terminology I am not familiar with. My old classics had a Lucas distributor and a separate coil setup.
    Regards

  5. #5
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    Quote Originally Posted by methoni View Post
    Yes I meant small block , must have been a senior moment. I what I need to do is contact the engine supplier and get a definitive answer, to be honest its a terminology I am not familiar with. My old classics had a Lucas distributor and a separate coil setup.
    Regards

    Terminology is not exactly clear, by "Single Spark" do you mean a single spark souce (Coil) or a single coil per cylinder?

    If you have a distributor you will have a single coil providing sparks for all cylinders.
    If no distributor then you will either have one coil supplying pairs of cylindres, 4 coils for a V8, in wasted spark format or a coil per cylinder (coil on plug or coil near plug) which could also be understood as "Single Spark"
    CoP/CnP can work in sequential mode (each coil files only when needed, once per 2 revolutions) or in wasted spark format. Bit of a waste using coil per plug as wasted mode in my opinion as you are losing one of the main benefits (improved charge time) but some people do it to have neater HT wiring without having to implement an engine phase signal (usually from the cam)

    Your engine won't really dictate what system you have as it would be possible to (retro) fit wasted spark or coil per plug to an engine originally equipped with a distributor. However dding a distributor to an engine not originally equipped would be much more difficult and a complete waste of time as the best place for such medieval devices is in a museum or a bin (in my humble opinion of course)!

  6. #6
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    If you are running a dizzy then it will be single spark, EFI though will depend as said on the ignition system you run. I run Mega Squirt and this uses wasted spark, all it means really is it has 4 channels to fire the spark so operates them in pairs, so it fires the one that needs it and probably the one that is at the end of the exhaust stroke (opposite end of firing order) at the same time. One is required the other is wasted hence the name. Hope this makes sense.
    Martin

    351W 416.7 HP and 466.8 ft-lbs

    Running Mega Squirt and Edis 8


  7. #7
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    It’s got a HEI distributor supplied by summit racing ref 141_682 with an integral coil. I think that points to a single spark ignition setup. Anyway I have sent an e mail to summit racing for their advice.

  8. #8
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    Quote Originally Posted by methoni View Post
    It’s got a HEI distributor supplied by summit racing ref 141_682 with an integral coil. I think that points to a single spark ignition setup. Anyway I have sent an e mail to summit racing for their advice.
    Defo single spark
    Steve Brown

    CRC Regional Rep - East Anglia

  9. #9
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    Yes single spark
    Martin

    351W 416.7 HP and 466.8 ft-lbs

    Running Mega Squirt and Edis 8


  10. #10
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    defo not wasted spark - will be single spark:

    Wasted spark - Wikipedia
    Conny - A Carnival Red Metallic (paint code Ref: Jag CGG/1811) Southern Roadcraft V8 ( SRV8 ) with 383ci stroker chevy.

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