News

275 GTB4 engine assembly manual

Discussion in 'Vintage (thru 365 GTC4)' started by technician483, Nov 28, 2018.

  1. technician483

    technician483 Rookie

    Dec 30, 2014
    5
    Chelmsford, UK
    Full Name:
    Simon Raw
    I am in the process of setting up a pair of distributors and doing other engine work on a 275 GTB4 and am hopeful someone may be able to help out with a pdf copy of the 275 GTB4 engine assembly manual.

    If anyone has access to this I would be very grateful if they could help out.
     
  2. DWR46

    DWR46 Formula 3
    Honorary

    Jun 19, 2012
    1,100
    The 4 Cam Engine Manual has nothing in it about the distributors. It only shows the basic static and max advance settings for the S85A units. These are the same units as used on late 250 and 275 single cam motors. however, a number of 4 Cams were built with S85E distributors. They are 9 degree units instead of the normal 15 degree S85A.
     
  3. per904

    per904 Karting

    Feb 28, 2009
    76
    switzerland
     
  4. per904

    per904 Karting

    Feb 28, 2009
    76
    switzerland
     

    Attached Files:

  5. turbo-joe

    turbo-joe F1 Rookie
    Silver Subscribed

    Apr 6, 2008
    4,657
    southwest germany
    Full Name:
    romano schwabel
  6. John Vardanian

    John Vardanian F1 Rookie

    Jul 1, 2004
    2,610
    San Francisco Area
    Full Name:
    John Vardanian
  7. technician483

    technician483 Rookie

    Dec 30, 2014
    5
    Chelmsford, UK
    Full Name:
    Simon Raw
    Many thanks for all help.

    We have S85E distributors so the S85A advance curve doesn't really help.

    The distributors are currently not achieving full advance until 8000 RPM (engine) so will need to be adjusted. It seems like there has never been an advance curve printed for these distibutors so I will concentrate on ensuring maximum advance is achieved by a sensible engine RPM.

    Once again thanks for all help.
     
  8. DWR46

    DWR46 Formula 3
    Honorary

    Jun 19, 2012
    1,100
    Here is the correct theoretical advance curve for S85E distributors:
    600 distributor rpm = 0 degrees advance
    700 = 0
    800= 0
    900 = 1.5
    1000 = 3
    1100 = 3.5
    1200 = 4
    1300 = 5
    1400 = 6
    1500 = 6.5
    1600 = 6.5
    1700 = 7
    1800 = 7.5
    1900 = 7.5
    2000 = 8.5
    2500 = 8.5
    3000 and up = 9
     
    of2worlds likes this.
  9. turbo-joe

    turbo-joe F1 Rookie
    Silver Subscribed

    Apr 6, 2008
    4,657
    southwest germany
    Full Name:
    romano schwabel
    you are sure with this?
    only 9° at 3000 rpm from the distributor?. this then would be a max. advance from 18° at the crankshaft. a little less I think?

    and simon: thx for filling out your profile :)
     
  10. DWR46

    DWR46 Formula 3
    Honorary

    Jun 19, 2012
    1,100
    Joe: The flywheels on these engines are marked AF24. They use 24 degrees of static advance. This still gets you to 42 degrees total advance. I could write a novel on all this with the 4 Cam engines, but the late 4Cams (about after 10,000) mostly came with S85E distributors. The factory was trying to correct the fact that the 4 Cams made less power than the six Carb 2 Cams. By adding a lot of initial advance, they were trying to make the car accelerate better from low rpm. 4 Cams also had two different carb setups, one with 29mm chokes and one with 32mm chokes. These cars run best with S85A distributors and 32mm chokes.
     
  11. DWR46

    DWR46 Formula 3
    Honorary

    Jun 19, 2012
    1,100
    And yes, I have seen 4 Cams with S85E distributors and AF10 flywheels; talk about SLOW! Lamborghini did the same thing for different reasons. Espadas and Jaramas usually run about 20-22 degrees static advance in European form, but use a distributor that calls for 6 degrees static in USA emissions spec. My car came from the factory with a European Distributor and a USA flywheel!! Getting all that set correctly really woke it up!
     
  12. turbo-joe

    turbo-joe F1 Rookie
    Silver Subscribed

    Apr 6, 2008
    4,657
    southwest germany
    Full Name:
    romano schwabel
    have not known the static advance already has been 24°. you are sure so much? I don´t know any other engine with so much static advance. but then it makes sense only to have those 18° more
     
  13. technician483

    technician483 Rookie

    Dec 30, 2014
    5
    Chelmsford, UK
    Full Name:
    Simon Raw
    I can vouch for the 24 degrees static advance. We have the correct AF24 flywheel so will set at 24 degrees static.I will check our carburettor choke sizes as I wasn't aware there were 2 different carb set ups used.
     

Share This Page