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Thread: Spark Plugs choices for 67S

  1. #1

    Spark Plugs choices for 67S

    My 67S with the stock ignition came with the Bosch W5DC spark plugs when I got it, but the documentation talks about the W3DPO. I now need to replace them and was wondering what to get.

    I am also thinking about switching to a CDI unit. Would that change the choice of the plugs?

    1967 911S

  2. #2

    IMHO, the W3DPO plugs are too cold for these engines unless they are being driven flat out for a long time.

    You can get away with those plugs if the car has an MSD ignition system and matching coil.

    I would use W5DS with either ignition setup for all-around usage and W4DS for track use. These are silver plugs and have a very wide heat range.
    Steve Weiner
    Rennsport Systems
    Portland Oregon

  3. #3
    I cann't seem to find the Bosch silver plugs anywhere. They must have been discontinued. What is the downside of running cold plugs beside the big price difference?
    1967 911S

  4. #4
    Running plugs that are too cold for the application results in poor running and a loss of power.

    The silvers are usually a special order and few outfits stock them. Its a real shame as they are really better than the old style platinums (DPO).

    If you cannot find them, please e-mail me directly and I'll get you a set.
    Steve Weiner
    Rennsport Systems
    Portland Oregon

  5. #5
    I couldn't agree more. I've used nothing but the silver plugs for years. THey last longer than the old platinums, and cost much less. I've not tried to buy any for a while, so if they are becoming hard to get, please let me know where to find them!

    Relative to the heat range (W3, W4, etc), that's independent of the electrode material. I also agree that a W3 is a bit cold for anything other than racing, but I would probably not go beyond a W4.


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