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348 valve timing

Discussion in '348/355' started by ceraldesign, Feb 2, 2015.

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  1. ceraldesign

    ceraldesign Rookie

    Oct 28, 2006
    40
    #1 ceraldesign, Feb 2, 2015
    I would like to redo the valve timing on the 348 engine so that I can get more torque at the bottom end (2,3,4, gears ) , has anyone tried this, also I think the 348 challenge cars had a different valve timing
     
  2. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    9,727
    #2 Mitch Alsup, Feb 2, 2015
    Time the cams for more overlap, equally.
     
  3. ceraldesign

    ceraldesign Rookie

    Oct 28, 2006
    40
    #3 ceraldesign, Feb 2, 2015
    Thanks
     
  4. INTMD8

    INTMD8 F1 Veteran
    Owner Silver Subscribed

    Jun 10, 2007
    6,766
    Lake Villa IL
    #4 INTMD8, Feb 2, 2015
    Mitch is correct though you may run into issues with emissions if you need to get tested.

    Advancing the intake cams will accomplish this. You would end up with more overlap and earlier intake valve closing. Earlier intake valve closing shifts power earlier in the rpm range and increases dynamic compression. (at the cost of higher rpm power)

    In my opinion, I wouldn't bother with trying to make power earlier as it's easier to just shift later. (That and the entire engine in terms of intake runner length, headers/etc was designed around it's current powerband).
     
  5. ceraldesign

    ceraldesign Rookie

    Oct 28, 2006
    40
    #5 ceraldesign, Feb 3, 2015
    ok, but I was told that the challenge cars had different valve timing, that would help them come of the corners more aggressively, was I misinformed? but lapping the car it does take a while to spool up, I only vintage race the car and I definitely need more bottom end
    thanks
     
  6. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,614
    The Brickyard
    Full Name:
    The Bad Guy
    #6 ernie, Feb 3, 2015
    Last edited: Feb 3, 2015
    From what I have been told, the Challenge cars were allowed to run Euro cam timing.

    The non cat timing specs should move the power a bit lower in the rpm range.
    IIRC?
    Intake opens 14° before TDC
    Exhaust opens 53° before BDC
    Someone please correct me if I'm wrong.

    As for getting more bottom end "oomph" a set of FabSpeed headers will serve you well. Free flow cats, and free flow exhaust will help release some more ponies too. Get your throttle body's ported by Fchatter RobZ. Take the intake to a head shop and have the intake runners ported to match the outlet on the bottom. DO NOT open the outlet. You want the "Venturi" removed from the bottom-ish inside of the runner.
     
  7. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    9,727
    #7 Mitch Alsup, Feb 3, 2015
    Challenge 348s got the higher <ratio> drop gear set.
     
  8. vvassallo

    vvassallo F1 Veteran

    Aug 4, 2006
    8,325
    Palos Verdes
    Full Name:
    Vince V
    #8 vvassallo, Feb 3, 2015
    You mean the Speciale gear set? ;)
     
  9. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,614
    The Brickyard
    Full Name:
    The Bad Guy
    #9 ernie, Feb 3, 2015
    Actually the Spider gearing. :p
     
  10. Brewman

    Brewman Formula Junior

    Apr 3, 2012
    417
    NC Mountains @ Boone
    Full Name:
    Joe
    #10 Brewman, Feb 4, 2015
    Just curious, how many degrees can you advance cam timing from spec. before valves contact Pistons ? Thanks

    Brewman
     

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