4" stroke 4.130 bore vs 3.9" stroke 4.175 bore

Discussion in 'Engine Topic' started by phantom69, Mar 8, 2021.

which setup be best for a mostly street application

Poll closed Apr 7, 2021.
  1. 4.130 bore 4" stroke

    1 vote(s)
    20.0%
  2. 4.175 bore 3.9" stroke

    4 vote(s)
    80.0%
  1. phantom69

    phantom69 Member

    Messages:
    37
    Likes Received:
    0
    Joined:
    Dec 16, 2020
    all things being equal which of these combos be the best for longevity and ease on the motor in a mostly street driven setup

    cam 227int./238exh @.50 lift 116.5 LSA if you wanna get technical
     
  2. G72Zed

    G72Zed Veteran Member

    Messages:
    3,059
    Likes Received:
    1,526
    Joined:
    Sep 8, 2015
    Location:
    Canada
    If the bores are stable and ring seal is not compromised, I like the 3.900 stroke with the 4.175 (427.13 ci) bore in most all cases. Even better the 3.5 or 3.625 crank in a large bore.

    If your pushing the bore thickness limits with the 4.175, and looking for tire melting (ave.) TQ in the lower rpm's, the 4.00 x 4.130 (428.7) is ahead, as long as the pin is not in the oil band.

    Looking at the cam, is this an LS build??
     
  3. phantom69

    phantom69 Member

    Messages:
    37
    Likes Received:
    0
    Joined:
    Dec 16, 2020
    you could say that it is an LS build yes and no..its gonna be a certified freakshow if i can pull it off!
     
  4. G72Zed

    G72Zed Veteran Member

    Messages:
    3,059
    Likes Received:
    1,526
    Joined:
    Sep 8, 2015
    Location:
    Canada
    Is it a Dart Gen 1 block for the LS head type build ?
     
  5. phantom69

    phantom69 Member

    Messages:
    37
    Likes Received:
    0
    Joined:
    Dec 16, 2020
    its a manhattan project i cant give out such details its not that tho
     
  6. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

    Messages:
    16,457
    Likes Received:
    1,261
    Joined:
    Mar 25, 1999
    Location:
    San Jose, CA, USA
    The short answer: assuming you are staying within good machining tolerance, the larger bore is almost always better.
    Larger bore's unshroud valves and increase displacement without increasing piston speed.
     

Share This Page