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Thread: Problems with plug wire lengths and routing

  1. #1

    Problems with plug wire lengths and routing

    My new set of plug wires have different lengths then the originals and thus create a bit of a mess with routing them.

    That being said I don't know the official plug wire paths and restraint methods.

    Therefore I have 3 questions:

    1: Does anyone know the original lengths of the wires? (elbow to tip)
    2: Does any one have good pics of the original cable paths and restraints?
    3: Is there any problem with reducing the wire lengths? The new cables have screw on elbow connectors at the spark plug end.

    Any advice would be appreciated.

    Thanks in advance.

    Bob
    Attached Images Attached Images     
    1970 911S Targa
    On the road again soon.

  2. #2
    Just a pessimistic guess but like most things these days (see Stoddard Dash thread) I suspect mfg.s are taking advantage of cheap labor in China and although we are paying the legacy OE prices we are getting poor (some times ridiculous) quality. I am pretty sure Porsche or Stoddards for that matter are aware of what they are buying and who is making it and if one out ten is returned it is still worth it.
    Early 911S Registry #750
    1970 911E - The Good Stuff
    2001 Toyota Landcruiser

  3. #3
    Oh Yes,

    The engine is a 70 MFI and the new wires are Beru (German. But perhaps not made there)
    1970 911S Targa
    On the road again soon.

  4. #4
    The Beru connectors you have at the plug end are the 'wood screw' type. You can shorten any of your wires by literally unscrewing it from the connector, cutting it off and screwing it back in. Hopefully your new wire is an old fashioned copper core type rather than some carbon conductor fluff so that the wood screw has something good to bite into as intended. For 911's the Beru connectors have resistors in them, so the wire used was plain copper core non-resistor wire. In your pictures, that particular model Beru spark plug end connector contains a 1000 ohm resistor. Note that your top three wires have a different distributor end connector than the bottom three. The top three have a 1000 ohm resistor connector at the distributor end as well. That type of connector also has the 'wood screw' metod of attachment. The bottom three in your picture have a plain rubber non-resistor end with a crimp on attachment. A 'less robust' type of wire set...

    The type with resistors at both end is 'more correct'. The reasoning was that since the wires on a 911 vary in length a lot, using resistor wire would vary the resistance on each lead depending on the length. So they used plain wire with no resistance and put resistors at both ends so all wires were the same.

    I have found if you use the factory specified lengths, the wire set comes out just plain too long, especially on the left side. I've ended up just trimming them until it 'looks' right.

    There is really nothing to wear out with the connectors in your old set. They can easily be reused, and checked with an ohm meter to prove they are good. Those are by far the most expensive part of a new wire set, and every time someone does this, their old ones were probably perfectly fine. You can make, in essence, a brand new set for a few bucks worth of wire and a couple of hours in the garage.

    So all you have to do to make a perfectly good new set is buy some good old copper core wire (fortunately the cheapest kind to buy), cut them to length and screw them into your old connectors. There are also improved Beru connectors from later cars that use a nice 8mm long threaded connector on the spark plug end instead of the wood screw type. A threaded male connector is crimped on the wire end and screws into the spark plug connector. With these, the wire can be easily be removed and reconnected any time in order to thread the wires through the factory wire dividers, under manifolds, etc. aside from just looking like a better and stronger method of attaching than the wood screw type.
    John Gray

    70 old air
    86 middle air
    95 new air

  5. #5
    John Gray

    70 old air
    86 middle air
    95 new air

  6. #6

    Old set + new set = good set?

    Thanks John,

    That was really informative.

    In pursuit of possibly saving a few bucks I disassembled my old cables and measured the resistance of the 6 spark plug connectors and 7 connectors at the distributor cap. This is what I found.

    Spark plug connectors: 4 at 0 ohms. 2 at 1000 ohms.
    Distributor Connectors: 7 at 1100 ohms.

    So what I will do now is add the distributor connectors to the new wire set and I should be in good shape. I will have the 1K ohm distributor resistance and the 1k ohm spark plug resistance which was the original spec.

    Glad I didn't chuck the old wire set. :-)
    1970 911S Targa
    On the road again soon.

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