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Idle Speed?

Discussion in '206/246' started by John Corbani, Jul 31, 2008.

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  1. John Corbani

    John Corbani Formula 3
    Honorary Owner

    May 5, 2005
    1,153
    Santa Barbara, CA
    Full Name:
    John Corbani
    #1 John Corbani, Jul 31, 2008
    I set my idle speed at 1000-1100 RPM and have no problem with plugs fouling. NGK 7 heat Iridium. I have left the car idling for half an hour during a photo shoot and not a miss. If I try for 800 RPM then engine sometimes just stops. No reason but car is unreliable at that speed. Car is USA '72 246 GT. All smog gear removed. One set of points in distributor. Advance curve per European specs. Dinoplex is out and replaced with basic Perma Tune. Original coil. Car runs right up to the redline and no erosion of the plugs. Plugs look great when checked every couple of thousand miles. Current plugs are at 14,000 miles and are still perfect.
    Just read a mention of someone complaining of NGK 7 heat plugs loading up at idle and someone suggested 6 or even 5 heat range. NGK specs 7 for all Ferraris that use this size plug. I worry about the top end, not the bottom when selecting plugs. Preignition could be deadly in that engine. Particularly with low octane gas. Be aware that NGK heats are the reverse of Champion, etc. Wondered what others use as plugs, the heat range and the idle speed. Please chime in.
    John
     
  2. johnvwatts

    johnvwatts Formula Junior

    Jul 7, 2007
    522
    England
    Full Name:
    John v watts
    #2 johnvwatts, Aug 1, 2008
    Last edited: Aug 1, 2008
    Hi John. Re the plug issue. My car only tends to foul up when first starting and running it out of the garage . In traffic it seems fine. Picked up the plug issue from the 308 section where they found nkg 6's best. I think when Ferrari state the plug spec its on the basis of factory spec jet sizes. So I guess that needs checking. But I have found the hotter plugs much better in both my 512bb and 308 gtb as they both have much richer jets and the standard plugs can foul. Having said that there turned out to be another reason for the fouling which was some green crud on the plug lead ends and in the distributor (worth checking). Take your point on car running to hot in the combustion chamber. Guess is just a trial and error thing. If yours are running a nice grey colour then there're probably ok.

    Re tickover RPM. I also have mine set at about 1200 and 800 seems to low on mine also. But my car has a none standard cam which means its difficult ie lumpy to run at 800rpm.

    Anyone?
     
  3. jselevan

    jselevan Formula 3

    Nov 2, 2003
    1,873
    #3 jselevan, Aug 1, 2008
    John and John - I try to set my idle at the lowest RPM that will sustain smooth running. With a little attention to the idle mixture jets I can set it at 400 RPM without difficult. No reason to do so, but it does allow me to tune in the mixture much more accurately. The lower the idle speed, the more each cylinder will impact smooth/rough running if the mixture is off in one cylinder.

    I agree with John W. on this issue of inspecting the distributor cap. I just had an educational experience with my Boxer (suggest you read the "Uncommon but hidden problem" thread. Car was running terribly. Thought it might be injection issues. Took off the distributor cap only to find a swamp of rain forrest, water, mist, and green copper oxidation everywhere. Cleaned it up and the car runs like never before. It must have been damp in the cap for years.

    Jim S.
     
  4. TonyL

    TonyL F1 Rookie

    Sep 27, 2007
    4,202
    Norfolk - UK
    Full Name:
    Tony
    #4 TonyL, Aug 2, 2008
    Last edited: Aug 2, 2008
    Try the linkages to carbs, any play can gives bad idle.

    Check for fuel spillage through the main ports, incorrect float level can cause this and incorrectly set air bypass screws.

    I use NGK BPES7 plugs, these work great wiith Shell Optimax.
     
  5. John Corbani

    John Corbani Formula 3
    Honorary Owner

    May 5, 2005
    1,153
    Santa Barbara, CA
    Full Name:
    John Corbani
    #5 John Corbani, Aug 2, 2008
    Last edited: Aug 2, 2008
    I drive my car every day in every weather. Chokes have been disconnected forever. I set idle so it is good no matter what. Santa Barbara never gets too hot or too cold for long but can go from 40 F to 100 F from morning to afternoon. Car goes from cold to fans running. I can get the idle down after warming up but that is not the point. I was looking for a general running number that others have found reliable day in and day out.
    John
     

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