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12 V 71 N Detroits potential tune up question

Discussion in 'Engines' started by dennismc, Mar 24, 2017.

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  1. dennismc, Mar 24, 2017
    #1
    dennismc

    dennismc Senior Member

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    Considering getting both tuned up, talked to local mechanic re, settings etc specially on the timing issue,
    injectors are N65 brown tag, indicating advanced timing, mechanic says most are actually set a bit retarded, helps quicker warm up and overall better engine performance.

    Most of my tune up experience is with autos in the old days, so am real curious as to the legitimacy of this claim, any specific experience out there would be appreciated.
  2. Capt J, Mar 24, 2017
    #2
    Capt J

    Capt J Senior Member

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    The tune up, I would go with the specs in the book. However there is a set of covington 12v71TI's that use a generator injector height setting of 1.46, if you set them to the marine engine setting (I think it was 1.98) they black smoke like crazy throughout the rpm range. Measure them before they reset them and you should know pretty much where they were when you look in the book.
  3. baltimore bob, Mar 24, 2017
    #3
    baltimore bob

    baltimore bob Member

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    Is the engine spec tag still on one of the rocker covers? If so, the injector height (timing) will be listed. My 6 71Ns run N80 injectors at 1.46 with absolutely no smoke. The 2 critical "tune up" items are adjust the rack, to ensure all cylinders are fueled evenly and injector height (timing). While you are in there you might as well check the exhaust valve adjustments.
  4. Capt Ralph, Mar 24, 2017
    #4
    Capt Ralph

    Capt Ralph Senior Member

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    Detroit Rule #1; Never kick a sleeping dawg.
    For those in Rosalinda; If it's not broke,, don't fix it.

    So why do you think you need a tune up? Smoke color? lack of performance? Want to throw money at a problem that does not exist?
    Want to induce a problem that will cost you more money to fix?

    I'm also leery of any mechanic who wants to alter factory specs.

    N65 brown tag turbo use 1.484 timing.
    N65 Brown tag non turbo with advances cam use 1.484 timing.
    If the non turbo engine does not have an advanced cam, use 1.460 timing for the N65 brown tag.
    It is the factory recommendation if you insist on using these N65 injectors to advance the cam and time @ 1.484.
  5. dennismc, Mar 24, 2017
    #5
    dennismc

    dennismc Senior Member

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    Need to replace one leaking injector tube, usually a tune is done after head re and re etc..all 6 on one side will be done, so am doing some pre work investigation.
  6. Capt J, Mar 24, 2017
    #6
    Capt J

    Capt J Senior Member

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    I'd take a REALLY hard look at all 6 injector tubes. If they look suspect in the least, I'd replace all of them.
  7. dennismc, Mar 24, 2017
    #7
    dennismc

    dennismc Senior Member

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    Thats what i said doing all 6..only one is bad, but the heads off so do them all. it's only a days work..
  8. Capt J, Mar 25, 2017
    #8
    Capt J

    Capt J Senior Member

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    I meant, if any others look suspect, I'd yank the other cylinder head off and do those too.
  9. Capt Ralph, Mar 25, 2017
    #9
    Capt Ralph

    Capt Ralph Senior Member

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    Sorry, I did not catch that on post #1.
  10. dennismc, Mar 25, 2017
    #10
    dennismc

    dennismc Senior Member

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    No worries other side all looks good. I check them all annually just in case can be expensive if one leaks water.