Undersquare vs. Oversquare Engines

Discussion in 'Mopar Performance Issues' started by ramcharger, Jan 8, 2009.

  1. famous bob

    famous bob mopar misfit

    Messages:
    10,253
    Likes Received:
    2343
    Joined:
    Aug 14, 2011
    Location:
    okla
    Local Time:
    3:25 PM
    dis agree , a 750 horsepower engine w/ 700 ft lbs of torque would kill it , in the same weight car, w/ traction.
     
  2. 67Dart273

    67Dart273 Well-Known Member

    Messages:
    37,524
    Likes Received:
    5228
    Joined:
    Oct 14, 2010
    Location:
    Idaho
    View My Photos
    Local Time:
    1:25 PM
    No, opposite. A short stroke big bore engine is "oversquare"
     
    • Agree Agree x 1
    • 273

      273 Well-Known Member

      Messages:
      2,801
      Likes Received:
      607
      Joined:
      May 14, 2012
      Location:
      Ontario
      Local Time:
      4:25 PM
      I disagree lol

      Torque at the crank don't matter its torque to the ground, if geared right both would have similar torque to the ground (actually hp).
      Which one that had the better hp curve should win. But with the F1 engine it would be hard to find a deep enough gear and high enough stall lol.
       
    • rumblefish360

      rumblefish360 so close yet so far away

      Messages:
      32,109
      Likes Received:
      4375
      Joined:
      Jun 21, 2005
      Location:
      New York, on a Island
      View My Photos
      Local Time:
      4:25 PM
      Naaaa, it can be done
       
    • MOPAROFFICIAL

      MOPAROFFICIAL Well-Known Member

      Messages:
      2,334
      Likes Received:
      1332
      Joined:
      Jun 1, 2016
      Location:
      breakwater
      Local Time:
      1:25 PM
      This is like 440 vs 426 hemi but not ,but like....

      Gear the short stroke motor and it's heads even in the constraints given will out flow and power the sb offering .

      Same heads, literally, then the stroke will poke.
       
    • AJ/FormS

      AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

      Messages:
      14,129
      Likes Received:
      3563
      Joined:
      Jan 19, 2014
      Location:
      South-Central Manitoba,Canada, 900ftelevation
      View My Photos
      Local Time:
      3:25 PM
      Here's food for thought; all are about 344 cubers, and all SBMs
      4.06x3.315....3.91x3.58.....3.80x3.79.....3.70x4.00
      Put the same small-valve heads on each of them, for obvious reasons.
      Which would you rather have?
      Well that depends on the application....right?
      But optimize the valves and then what?
       
      Last edited: May 13, 2018
    • 67Dart273

      67Dart273 Well-Known Member

      Messages:
      37,524
      Likes Received:
      5228
      Joined:
      Oct 14, 2010
      Location:
      Idaho
      View My Photos
      Local Time:
      1:25 PM
      426 hemi has the same stroke as any RB engine so ??????

      You are talking strictly the difference in heads / piston dome? Then yeah.
       
    • rumblefish360

      rumblefish360 so close yet so far away

      Messages:
      32,109
      Likes Received:
      4375
      Joined:
      Jun 21, 2005
      Location:
      New York, on a Island
      View My Photos
      Local Time:
      4:25 PM
      And then.....

      The hair splitting!!! And, one upmenship, but's, what if's, bigger that, recontoured this, I can do this, I can do that, I get better with this.....

      OMG! IT'LL never end!!!!
       
    • 69conv

      69conv leaky gasket FABO Gold Member

      Messages:
      1,729
      Likes Received:
      954
      Joined:
      Jan 27, 2013
      Location:
      Motor City
      View My Photos
      Local Time:
      3:25 PM
      I had a friends who's cousins uncle...
       
    • famous bob

      famous bob mopar misfit

      Messages:
      10,253
      Likes Received:
      2343
      Joined:
      Aug 14, 2011
      Location:
      okla
      Local Time:
      3:25 PM
      Smoked pot ?
       
      • Like Like x 1
      • yellow rose

        yellow rose Doctor of Thinkology.

        Messages:
        15,415
        Likes Received:
        11996
        Joined:
        Jun 19, 2015
        Location:
        Living on the razors edge
        Local Time:
        1:25 PM

        I always opt for the bigger bore. Then gear accordingly.
         
        • Like Like x 1
        • Agree Agree x 1
        • famous bob

          famous bob mopar misfit

          Messages:
          10,253
          Likes Received:
          2343
          Joined:
          Aug 14, 2011
          Location:
          okla
          Local Time:
          3:25 PM
          thot they were supposed to be the same except the engine ! Torque is what gets u moving.
           
        • famous bob

          famous bob mopar misfit

          Messages:
          10,253
          Likes Received:
          2343
          Joined:
          Aug 14, 2011
          Location:
          okla
          Local Time:
          3:25 PM
          Not according to bill Jenkins, get one of his race trick books and read it. I didn`t care for him, but he was a pretty darn smart guy.
           
        • 273

          273 Well-Known Member

          Messages:
          2,801
          Likes Received:
          607
          Joined:
          May 14, 2012
          Location:
          Ontario
          Local Time:
          4:25 PM
          Both basically have the same torque, theres no free lunch. The 700 lbs-ft engine is obviously twice the size and turn half the rpms then the 350 lbs-ft engine. So for every one revolution of the larger engine the smaller one is doing two. Torque is basically a snapshot of one revolution and hp is them all added up over time. So if you look at both engines here there both doing 700 lbs-ft in the same moment. 1 x 700 = 700, 2 x 350 = 700.

          To access the smaller engine potential we would need about twice the gearing which would put the same torque to the ground.
          So both engines have the same hp and torque. Again the better hp curve should win.

          Thats why we use hp to compare motors it takes acount of all the torque an engine produces not just one revolution.
           
          Last edited: May 14, 2018
        • famous bob

          famous bob mopar misfit

          Messages:
          10,253
          Likes Received:
          2343
          Joined:
          Aug 14, 2011
          Location:
          okla
          Local Time:
          3:25 PM
          Don't agree w/ gearing making torque the same . Lookat a trctor, small low h.pand low torque engines w/ wild gearing, they still don't have any torque. TORQUE AND GEARING AINT THE SAME THING !
           
        • rumblefish360

          rumblefish360 so close yet so far away

          Messages:
          32,109
          Likes Received:
          4375
          Joined:
          Jun 21, 2005
          Location:
          New York, on a Island
          View My Photos
          Local Time:
          4:25 PM
          I agree. IMO, I think 273 spends to much time inthe calulators like AJ. Real world suggests otherwise.... OH wait, sporty, proves otherwise.
          Application dependent of course....
           
        • 273

          273 Well-Known Member

          Messages:
          2,801
          Likes Received:
          607
          Joined:
          May 14, 2012
          Location:
          Ontario
          Local Time:
          4:25 PM

          Cause a tractor has no power. Gearing can't create power. It can only get you into the powerband. The ultimate gearing would be a variable transmission that would keep you at peak hp through out the 1/4 mile. Or any high work loads. Thats why rock crawllers run crazy gearing so to be up in the powerband (hp) while driving at low speeds.

          But both of the above engines (700 vs 350 lbs-ft) have the same power. Just different torque. And if you gear them optimally for the 1/4 you'll out they'll have similar torque to the ground. But really more important be at similar hp per mph, given them similar power to the ground depending on the hp curves.

          Cause you get nothing for free. When you build to wildly different displacement engines to the same hp one is gonna trade rpm for torque and the other is gonna do the opposite. And If rpm wasn't just as valuable as torque for the reasons I explained earlier. It wouldn't be apart of the hp formula.
          The 5252 part is mainly to convert the engines power to compare with horses leaving torque and rpm to explain your engine power.

          If torque plays a big role in quarter mile times how come there no formula or rule of thumb etc.. for optimal torque ?
          We all know power to weight does.
           
        • famous bob

          famous bob mopar misfit

          Messages:
          10,253
          Likes Received:
          2343
          Joined:
          Aug 14, 2011
          Location:
          okla
          Local Time:
          3:25 PM
          Still off!, I grew up on a farm w/ 5 diff type tractors on it, they don`t have to be wide open to do their job, the powerband thing don`t cut it in them. One of our tractors had a 6 cyl. Chrysler car motor in it, it was scary fast on the road w/ no governor, another super M was as stout w/ a 4 cyl engine , but certainly not the fastest . As I SAID GEARING DOES NOT CREATE TORQUE, but will cover up a lack of...............
           
          Last edited: May 15, 2018
        • rumblefish360

          rumblefish360 so close yet so far away

          Messages:
          32,109
          Likes Received:
          4375
          Joined:
          Jun 21, 2005
          Location:
          New York, on a Island
          View My Photos
          Local Time:
          4:25 PM
          Just multiplies it!
           
          • Agree Agree x 1
          • 273

            273 Well-Known Member

            Messages:
            2,801
            Likes Received:
            607
            Joined:
            May 14, 2012
            Location:
            Ontario
            Local Time:
            4:25 PM
            A tractor really has no brearing on your original point. No amount of gearing will make it a top fuel dragster. Again gearing don't do much cause the engine has little power in the 1st place.

            Your original point was a 700 hp 700 lbs-ft will smoke a 700 hp 350 lbs-ft cause of the torque difference. Which I point out among other things if both geared properly for the 1/4 mile both will be putting similar torque to the ground nullifying the difference at the crank. But that only works if comparing two engines of the same/similar power.

            My point is you don't gain extra power by building 700 hp at a lower rpm then another engine making it at high rpm. Cause when setup right (stall gearing) the differences (torque) will be the same at the tire.

            Why cause your not gaining anything. Thats why they both make the same power. But the larger engine will trade rpm for torque and the smaller one do the opposite.
             
          • rumblefish360

            rumblefish360 so close yet so far away

            Messages:
            32,109
            Likes Received:
            4375
            Joined:
            Jun 21, 2005
            Location:
            New York, on a Island
            View My Photos
            Local Time:
            4:25 PM
            Oh jeeezzzzz
            :realcrazy::rolleyes::poke: