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Thread: Spark plugs on an early 65 Porsche 911 with Solex 40 PI carburetors

  1. #1
    Junior Member
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    Spark plugs on an early 65 Porsche 911 with Solex 40 PI carburetors

    Hello to everyone,

    after adjusting my Solex 40 PI carburetors with lots of help from Paul Abbott from performance oriented on my stock early 65 Porsche ( 300 357 ) and driving for about 60 Miles, I have the following picture taken of the spark plugs when I took them out of the engine.

    Car was running in different speeds and gears, in city traffic and also up to 7000 rpm. Engine temperature was good but not too hot 200 to 210 Fahrenheit ( between 90 and 100 degrees celcius, fuel has 98 octane, spark plugs are NGK BP 7 ES.

    Would you guys say, the plugs do look ok ?

    Thanks for any info.

    Greetings,

    Stefan

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  2. #2
    Hi Stefan , can you clarify which plug goes to which cylinder ?

    Next , were the plugs new and so have only done 60 miles ? That is not a lot of run time .

    If those sooty deposits have formed in 60 miles then they are definitely running rich and you need to tune the carburettor barrel by barrel .

    You dont mention how car was running ,,

    any backfiring on overrun
    any flat spots on acceleration
    any coughing on tickover

    Cheers

  3. #3
    Stefan,

    In lieu of other input I offer the following:

    Those plugs look pretty good to my eye but if you wanted to optimize then the following is a plan that could be used as a baseline for doing this yourself. A rolling road would be best/easiest but there's no fun in that!

    • Find a section of autobahn that allows a section of perhaps two kilometres with a place to exit so you can pull the plugs
    • Install a fresh set of plugs and make your run at near peak RPM in fourth (a more reasonable effort than in fifth)
    • At the end of the run, simultaneously de-clutch & kill ignition & coast to your designated stop
    • Pull plugs & inspect for rich/lean
    • For those cylinders that are rich, adjust turnbuckle to open that throttle by turning the turnbuckle 1/4 turn
    • For those that are lean, adjust turnbuckle to close that throttle by 1/4 turn
    • Re-install plugs & return to your starting position at the beginning of your test run
    • Install a new set of plugs and repeat your high speed run and plug inspection


    The above will provide a guide as to how effective the turnbuckle adjustment was and if the adjustments were of the right magnitude.

    Adjusting turnbuckles WILL affect the idling performance which will require re-adjustment using throttle stop screw and most likely idle mixture screws as well.

    As an alternate approach, one that would preserve idling and slow speed performance you could change jetting to create individually optimized jets for each cylinder. The main air correction jets are what I would select as they have minimal effect on transition and are more effective for WOT operation. A smaller main air correction jet will enrich mixture at WOT and conversely.

    Best of luck!
    Last edited by 1QuickS; 08-03-2020 at 02:43 PM.
    Paul Abbott
    Early S Member #18
    Weber service specialist
    www.PerformanceOriented.com
    info@PerformanceOriented.com
    530.520.5816

  4. #4
    Junior Member
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    Hello Paul,

    thanks for your very detailed procedure.
    I will try that the next couple of days here on the Autobahn very early in the morning since we have 6 weeks schoolholidays and people tend to drive during the daytime on the Autobahn. So lots of slow traffic and people who really cannot drive their cars make it hard to have a full bore run.

    I will post results and maybe some short video from RPM and Speed.

    Thanks again for appreciated comments and always being right on target.

    Also thanks to oldtimer for your fast reply.

    Greetings,

    Stefan

  5. #5
    Senior Member uai's Avatar
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    Hi Stefan, I would try to get an old/used exhaust manifold and add 6 M18x1,5 bungs then you can check for lambda individually for each cylinder with a wbo2 kit.

  6. #6
    Senior Member haul's Avatar
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    Uli is right,
    you have to set it up accordingly to the CO value of every single cylinder, even if you hang up a sensor during the drive in the exhaust the value might be not correct, as it always can be that 4 cylinders are running nicely and two are to lean, thus making a faulty result in the single exhaust.
    plug colors are no more the way to really tell the truth due to the changed mixtures of gasoline....!

    where are you located?
    dynodrive would be one step,
    which jets are you on, idle, main and air correction?


    br
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    63 650 gray silver bikinitub triumph thunderbird
    70 650 astralred silver triumph bonneville
    65 912 slate gray "erwin"
    73 914 ravennagreen "ferdl"
    erwin_loves_polo

  7. #7
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    Hello Uli, haul and Paul,

    sorry I get back so late but some other issues on my other cars came up which I had to attend first. I will take another chance on the 65 on Sunday on the Autobahn with new spark plugs and new set up. Uli, the idea of setting up the manifold like you mentioned is good and I have heard about it before. The problem is, you don't find the manifolds for those early cars with Solex 40 PI carburetors no easy and if, they cost you a fortune, because they are different from the later ones with the Weber 40 IDA our IDS.

    I will try to upload two short videos of my demo drive on the Autobahn. I was holding the iPhone with half a hand and try to keep the car on the road with the other 1,5 hands. At 7000 RPM and 210 KMH it is a bit shaky.

    Hope the videos will be uploaded here, I never tried this before.

    https://photos.google.com/search/_tr...Q1-YkBY0Sd_9E-


    https://photos.google.com/search/_tr...PkpRugHzmL3uwT[/VIDEO]



    Thanks,

    Stefan

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