Dwell Angle on a V12 | FerrariChat

Dwell Angle on a V12

Discussion in 'Vintage (thru 365 GTC4)' started by Ferrari_250tdf, Feb 5, 2010.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. Ferrari_250tdf

    Ferrari_250tdf Formula Junior

    Mar 3, 2005
    461
    #1 Ferrari_250tdf, Feb 5, 2010
    Last edited: Feb 5, 2010
    What would be the dwell angle on the Marelli distributors on a V12 e.g. a 275?

    Thanks for your help!

    Matthias
     
  2. Motob

    Motob Formula 3
    Professional Ferrari Technician

    Nov 11, 2003
    2,238
    Frederick, Maryland
    Full Name:
    Brian Brown
    50 degrees total, 25 degrees on each point set.
     
  3. TTR

    TTR F1 Veteran
    Rossa Subscribed

    Mar 29, 2007
    5,145
    Riverside, CA
    Full Name:
    Timo
    Daytona ?
     
  4. Bart340

    Bart340 Karting

    Mar 7, 2005
    66
    Netherlands
    Full Name:
    Bart Rosman
    50 degrees plus or minus 2 and not built up by two times 25 as suggested by Motob.
    Bart340
     
  5. TTR

    TTR F1 Veteran
    Rossa Subscribed

    Mar 29, 2007
    5,145
    Riverside, CA
    Full Name:
    Timo
    #5 TTR, Feb 8, 2010
    Last edited: Feb 8, 2010
    Each distributor with their respective points (R1/main on the U.S. Daytona) ?

    Brian (or any one else with extensive experience), do You agree ?
     
  6. Eagle1

    Eagle1 Rookie
    BANNED

    Feb 13, 2009
    48
    Wisconsin
    Full Name:
    Mark Poulter
    Hmm... I understood, for the 275, they require 48-50 deg. on each distributor...meaning, ~25 deg on each point set. However, the Daytona is different as it has 6 lobes instead of 3 found on the 275. This results in a smaller dwell angle
     
  7. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    37,986
    Clarksville, Tennessee
    Full Name:
    Terry H Phillips
    #7 tazandjan, Feb 8, 2010
    Last edited: Feb 8, 2010
    European Daytonas, like my old 14009, had two three lobe distributors, with two sets of points each, just like the earlier twin distributor street V12s. On the road, so cannot confirm the dwell.

    Taz
    Terry Phillips
     
  8. 335s

    335s Formula Junior

    Jan 17, 2007
    870
    SF Bay Area
    Full Name:
    T. Monma
    specifically, what engine are you asking, exact iteraation///
    s85a is used on LOTS of engine families...not all with same specs...
     
  9. f308jack

    f308jack F1 Rookie

    Jun 7, 2007
    4,300
    Cape Town, South Afr
    Full Name:
    Jack Verschuur
    The dwell angle for 2 3-lobed sets of points can be calculated, and should be around the 50- degree figure, or even a few degrees more.
     
  10. Bart340

    Bart340 Karting

    Mar 7, 2005
    66
    Netherlands
    Full Name:
    Bart Rosman
    As I said, factory information is 50 degrees plus or minus 2 (depending on the points gap), so 52 degrees can easily obtained. This is of course for a 3-lobe double points distributor.
    Bart340
     
  11. John Vardanian

    John Vardanian F1 Rookie

    Jul 1, 2004
    3,043
    San Francisco Area
    Full Name:
    John Vardanian
    Digging up this old thread...

    Can someone please explain how we have arrived at the 50 degrees total, 25 degrees per point set for the three-lobe, dual-points distributors? Thank you in advance.

    john
     
  12. DWR46

    DWR46 Formula 3
    Honorary

    Jun 19, 2012
    1,810
    John: The Marelli units are not like the American dual point distributors. On the Ferrari unit, each set of points operates independently and fires three cylinders. The American units link both sets of points together to increase the TOTAL dwell to get more coil saturation. I have never trusted dwell tachometers or Sun machines totally, so I adjust one set of points to a gap I like (usually about .015-.016" for the Marelli's) and then get a dwell reading for that point set. Then I adjust the other set of points to the same dwell reading. This procedure allows for variances in measuring methods and machines. By the way, the Marelli specs for the S85A distributor are 50 degrees PER SET OF POINTS for closing angle. This is NOT dwell. They also spec 10 degrees for the opening angle. Let me give you another example where Marelli actually gives spec for dwell. On a US Daytona with a six lobe cam, the spec is 32 degrees closing angle and 28 degrees opening angle for the primary set of points, yet the dwell spec is 53.5 degrees. Secondary points use slightly different settings. American six lobe distributors use about a 40 degree dwell setting. It is all about the shape of the distributor cam!!
     
    BMWairhead, enio45, readplays and 2 others like this.
  13. John Vardanian

    John Vardanian F1 Rookie

    Jul 1, 2004
    3,043
    San Francisco Area
    Full Name:
    John Vardanian
    Thanks for the explanation, Dyke. A .014" gap does produce a dwell of about 25 degrees on the distributor machine. Then, conversely, a dwell of 25 degrees does not necessarily give you a gap of .014" on the opposite set of points. As you said, the shape of the cam plays a part. It doesn't seem like the three peaks on the cam are exactly 120 degrees apart.

    john
     

Share This Page