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Discussion in 'Vintage (thru 365 GTC4)' started by 365GTC/4, Mar 30, 2008.

  1. 365GTC/4

    365GTC/4 Formula 3

    Apr 7, 2005
    1,429
    Melbourne, Australia
    Full Name:
    John
    Attention: Engine Experts
    I am in the midst of a valve adjust on a C4.
    The C4 manual states Inlet 0.10 to 0.15 mm Exhaust 0.25 to 0.30 mm clearence.
    Now 400 GT manual (basically same motor) states Inlet 0.20 to 0.25 mm Exhaust 0.30.to 0.35 mm. !! Why the larger clearence??
    Theory: "MAYBE" Ferrari found some problems in service with the former tighter tolerences. Now with the larger tolerences you maybe will increase valve train noise and decrease horsepower by a few percent but the up side is that you greatly reduce the risk of burning valves because they do not seat correctly to dissapate the heat.
    Another theory: The change was to improve pollution control??
    Any comments please. I will put in the new shims this week and I would like opinions on the above.
    Thanks
    John
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  3. Tinbender

    Tinbender Formula Junior
    Rossa Subscribed Owner

    Mar 13, 2004
    313
    Raleigh,Lake Lure,NC
    Full Name:
    Terry W. Phillips
    Hello John,
    The 400GT manual I have seen has the same clearances as the 365gtc4 but the 400i manual has the larger clearances.

    Regards,
    Terry Phillips
     
  4. Randy Forbes

    Randy Forbes Formula Junior

    Jul 14, 2006
    741
    Sarasota, FL
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    Sports Cars Plus,LLC
    Age-old adage is that loose valves will never cost you money...

    ... tight ones will!

    You should be comfortable setting them to the loose end of the spec for your chassis (365 GTC/4). You'll never notice any difference in performance.
     
  5. gsjohnson

    gsjohnson Formula 3

    Feb 25, 2008
    2,291
    Woodland Hills, CA
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    GS Johnson
    But loose ones wil cost you horsepower.
     
  6. Randy Forbes

    Randy Forbes Formula Junior

    Jul 14, 2006
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    Sports Cars Plus,LLC
    But, which is more easily afforded; who are you racing and what is the prize?

    ;)
     
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  8. open roads

    open roads F1 Rookie
    Silver Subscribed

    Jan 28, 2007
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    Stan
    Polution control was taking over.
     
  9. 2NA

    2NA F1 World Champ
    Professional Ferrari Technician Consultant Owner

    Dec 29, 2006
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    Tim Keseluk
    I'm with Randy. A little "clicking" is cheap insurance (you'll probably not notice the difference unless you're standing there with the hood open).

    I also doubt you'll notice any performance difference.

    Split the difference and set them carefully to the tight side of the looser spec.
     
  10. John Vardanian

    John Vardanian F1 Rookie

    Jul 1, 2004
    2,803
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    Actually, if you are in tune with your car you will notice the improved engine response of the tighter settings, at least with the inside plug engines. However, overall engine heat increase-- which can be a problem for some.

    john
     
  11. kare

    kare F1 Rookie
    Consultant

    Nov 11, 2003
    3,297
    I fail to see what is insured when expensive parts are clicking against each other. I always use the smallest values given by a manufacturer. They already include a safety margin and I never drive my cars particularly hard for a long time. Best wishes, Kare
     
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  13. 365GTC/4

    365GTC/4 Formula 3

    Apr 7, 2005
    1,429
    Melbourne, Australia
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    John
    Kare
    The insurance referred to is that if the gap is too small and the valve stem expands more than that figure when the engine gets real hot, then the valve will not seat. The valves get cooled when they seat but if they do not seat, then they overheat and fail. BANG = expensive. So to insure against that the idea is to use bigger gaps to allow for larger valve stem expansion due to heat, and still seat corretly, thus dissapate heat and thus stay in one piece.
    John
     
  14. Randy Forbes

    Randy Forbes Formula Junior

    Jul 14, 2006
    741
    Sarasota, FL
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    Clearly, you have a thorough understanding of the subject at hand. Good on you!
     
  15. kare

    kare F1 Rookie
    Consultant

    Nov 11, 2003
    3,297
    I know what is being referred to but it still is like wearing a condom when walking on the street. The values given by manufacturer always include a safety margin, and that margin safely sure as hell covers how these engines are driven today! Best wishes, Kare
     
  16. 2NA

    2NA F1 World Champ
    Professional Ferrari Technician Consultant Owner

    Dec 29, 2006
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    Tim Keseluk
    You know this how?

    Vintage Ferrari documentation frequently contains questionable data particularly when translated into languages other than Italian.
     
  17. 2NA

    2NA F1 World Champ
    Professional Ferrari Technician Consultant Owner

    Dec 29, 2006
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    I guess if it "feels" better it must be. LOL
     
  18. Bertocchi

    Bertocchi Formula 3
    Consultant

    Jan 28, 2004
    1,862
    New Orleans, LA
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    David Castelhano
    I think you need to know a bit my information. For instance the lift and duration of the cams used in the two different models. Historically Ferrari used different cams for pollution controlled cars and cars without pollution controls. Since 400s were never officially imported they could have very different valve timing specifications?
     
  19. tongascrew

    tongascrew F1 Rookie

    Jan 3, 2006
    2,989
    tewksbury
    Full Name:
    george burgess
    the valve clearances for the single cam V 12s hasn't changed much over the years. The 250/330 engines are intake.006"[.15mm] exhaust .008"[.20 mm]. I have just received the Jim Riff book "ferrari 250/GT Service and Maintenance. I recommend it as a primer for the mechanicly inclined but experienced lacking ferrari mechanic. The "how to" instructions are as basic and clear as you can get and the supporting drawings show it all. I would like to hear comments from anyone who has used this amnual. Is it as good as it appears??? Tongascrew
     
  20. John Vardanian

    John Vardanian F1 Rookie

    Jul 1, 2004
    2,803
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    One thing worth mentioning is that the clearance setting of a given valve isn't always an absolute. So, for instance, if you set an intake valve exactly at 0.006, rotate the roller some and gauge the gap again, in some cases your clearance will increase or decrease. This variation is due to the out of roundness of your roller. It's not enough to warrant replacing the roller, but it's enough make the feeler gauge "feel" the difference.

    I guess the moral of the story would be that if you'd like to set your valves on the tighter side to keep this little nuance in mind.

    john
     
  21. Fontana

    Fontana Karting

    Dec 30, 2006
    177
    Vermont
    Full Name:
    Peter Markowski
    Set your C/4 valves to the looser spec. We had a 400 that was set at the tight clearance (cannot remember exactly, I think .006 int, .008 exh) and the car never ran well. We loosened them to .008-.009 intake and .010-.012 exhaust and the car runs and starts much better and you still cannot hear the valves!
     
  22. 365GTC/4

    365GTC/4 Formula 3

    Apr 7, 2005
    1,429
    Melbourne, Australia
    Full Name:
    John
    John
    I have done multiple measurements and found differences of say +- 0.02 mm. I thought that it might be that the shims were not seating in the buckets correctly but your explanation of the lobe being slightly out of round is probably more likely.
    Thanks
    John
     

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