Fine tune cam indexing?? | FerrariChat
Buy

Fine tune cam indexing??

Discussion in '308/328' started by AZDoug, Jun 24, 2009.

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

  1. AZDoug

    AZDoug Formula 3

    Jun 17, 2009
    1,606
    Along the Verde , AZ
    Full Name:
    Doug
    #1 AZDoug, Jun 24, 2009
    Working from memory (been some years since I looked at the cam belts), I recall that there were a couple different ways to possibly index the cam sprockets to retard the cam or advance it, by some amount, depending on how the drive pins were placed.

    Is that correct, or am i mis remembering?

    If correct, it there some written guide as to which pin placements advance/retarded and how far the increment was?

    Next, does anyone make an adjustable cam sprocket for the 308? Sort of like the Cloyes Hex adjust timing chain gear, where you can advance or retard your cam in one degree increments, up to about 6 degrees either way, for optimized performance in certain RPM ranges?

    Thanks,
    Doug
     
  2. Mike C

    Mike C F1 Veteran
    Lifetime Rossa Owner

    Aug 3, 2002
    6,081
    Southeast USA
    Full Name:
    Mike Charness
    #2 Mike C, Jun 24, 2009
    Last edited by a moderator: Sep 7, 2017
  3. enjoythemusic

    enjoythemusic F1 World Champ

    Apr 20, 2002
    10,676
    Worldwide
    Full Name:
    Steven
    #3 enjoythemusic, Jun 24, 2009
    Mike, that was one of the tweaks i really regret not buying. Shoulda bought those for the 308 when it was here.
     
  4. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,805
    The twilight zone
    Full Name:
    Help me get this thing finished! https://gofund.me/39def36c
    #4 mk e, Jun 24, 2009
    The good news is the cam timing is infinately adjustable in 1 degree steps with the stock hardware. From memory 1 pin hole is 1 degree.

    The bad news is the stock timing (euro) is about ideal so there is nothing to be gained other than re-timing a US car to the euro specs.
     
  5. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,932
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #5 Steve Magnusson, Jun 24, 2009
    Last edited by a moderator: Sep 7, 2017
    It's difficult to build a fine adjustment into a compact range just in the cam-to-pulley mounting using the pin & hole method (because, for a reasonably-sized pin, the holes would overlap each other); however, by also "skipping" teeth in the belt, it's possible to spread things out. The attached chart shows how the 28 deg hole spacing in the cam, the 25 deg hole spacing in the pulley, and the 12 deg spacing between teeth on the belt (at the pulley) work all work together to give the 1 deg adjustment steps over a +/- 6 deg range (the distance between teeth on the belt), yet provide adequate physical spacing between the holes in the cam and sprocket.
    Image Unavailable, Please Login
     
  6. AZDoug

    AZDoug Formula 3

    Jun 17, 2009
    1,606
    Along the Verde , AZ
    Full Name:
    Doug
    #6 AZDoug, Jun 24, 2009
    Thank you. I suspected as much. I will have to study this and make sure I understand it. I do not plan on changing anything right now, this will be for the new cam grinds on the motor rebuild.

    Doug
     
  7. AZDoug

    AZDoug Formula 3

    Jun 17, 2009
    1,606
    Along the Verde , AZ
    Full Name:
    Doug
    #7 AZDoug, Jun 24, 2009
    I am in LOVE!!!!

    Who makes those?

    The cam possibilities with dual overhead cams are mindboggling.

    Instead of having the intake and exhaust lobes on one bumpstick, like my Chev pushrod motor, with fixed LSA's, you can vary not only the advance of the cam, but the LSA, also, to account for changes in exhaust and intake system, and vehicle usage/application.

    Thanks,
    Doug
     
  8. Ferraripilot

    Ferraripilot F1 World Champ
    Owner Project Master

    May 10, 2006
    17,919
    Atlanta
    Full Name:
    John!
    #8 Ferraripilot, Jun 24, 2009

    Changing the US cam timing intake open spec to Euro is just going to increase overlap a bit and raise the max power from about 6600 to 7000 right? I believe Euro manuals list max power at 7k as opposed to US which quotes 6.6k.
     
  9. 350HPMondial

    350HPMondial F1 Veteran
    Silver Subscribed

    Feb 1, 2002
    5,336
    18 mi from the surf,, close to Pismo, CA
    Full Name:
    Edwardo
    #9 350HPMondial, Jun 24, 2009
    Last edited by a moderator: Sep 7, 2017
    Doug,

    Scotty makes them, limited supply. (smg2 on this site.)
    Get yours now.....!
    You might need spacers, , ,and titanium washers.

    Then your gonna want a new front pully too.
    I make these....!
    Get it now, only two left. . . Gold or Red.

    http://ferrarichat.com/forum/showthread.php?t=228977

    Edwardo
    Image Unavailable, Please Login
    Image Unavailable, Please Login
     

Share This Page