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Thread: M. Marelli vs Bosch distributor 1971 question

  1. #1
    Senior Member Scott A's Avatar
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    M. Marelli vs Bosch distributor 1971 question

    I have two distributors, Bosch and M.Marelli. for 1971 T.

    I can look up the part numbers, later.
    I've been using the Bosch. Which I think is correct for a car made in 71.
    Earlier ones had marelli. (I also have Weber's)
    But I switch them up. To see what happens. It's free.
    Those are not the questions yet. I don't want to know which is correct.

    My question is technical. Mechanical. Scientific.
    When I use the marelli. I get a lot less popping out the exhaust. Almost none
    (Not popping out the carbs)

    My timing is the same on the pulley. 35 btdc. At 6k.

    Both distributors feel tight. (I know that is a variable)
    Both have nicely set points. Dwell. (I know that is a variable)

    Can the curve/cam really make a difference?
    It would seem the spark is instantaneous. And not hang longer.
    What else would make the marelli not pop?
    Last edited by Scott A; 07-15-2020 at 06:43 AM.

    Current long term ownership: 63 Cab, 71 911, 74 914

  2. #2
    Senior Member
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    71 911Ts used Marelli Distributors. There is NOTHING WRONG WITH MARELLI DISTRIBUTORS!!!!!!!!!!!!!!!!! They work great and are very reliable and long lasting. The "problem" with Marelli Distributors was not with the distributors but with mechancis and shop owners from a certain central European country that refused to believe that a distributor made in a country from the south of the certain central European Country could work in their "Superior" cars. Parts Klassic has gone to the trouble and expense of providing parts for all Marelli distributors. Kudos to them.

    Regards

    Jim
    I hope this doesn't get me bounced for some unforeseen reason.

  3. #3
    Does your Marelli dist. cap have the resistor ends and the Bosch doesn't?
    Early S Registry member #90
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  4. #4
    Senior Member Scott A's Avatar
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    I was using the same wires. Which are tall ends. And I believe have resistors.

    I forgot one variable. The advance curve from the weights.

    Current long term ownership: 63 Cab, 71 911, 74 914

  5. #5
    Yes, I understand the advance curve is different between the two, I was trying to eliminate other variables. You would need to have both tested on a distributor machine to see exactly where the curve differs. The biggest problem we had with Marelli's back in the 70's and 80's was wear in the advance weight pivots causing a slow return to idle. And yes Jim,,,P.K. does a nice job rebuilding them.
    Early S Registry member #90
    R Gruppe member #138
    Fort Worth Tx.

  6. #6
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    My original Marelli (in the basement) for my 71T has that exact issue, wear in the V of the advance weights, was unpredictable advance and backing down to idle, no parts 10 - 12 yrs ago so put in a Bosch E curve matched the rebuilt engine nicly, and back then the Bosch distributors were reasonable prices so picked up the S version (007?) liked it a bit better and it is still in the car. I should call Kurt and get a set of weights & springs on general principal.
    Thanks for the update on parts.

    Regards

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