4.375 VS 4.15 stroke Hemi

Discussion in 'PSI Superchargers Tech Questions' started by moparchris440, Dec 2, 2016.

  1. moparchris440

    moparchris440 Member

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    I've ran a 4.375 crank with a 4.375 bore 526ci BAE standard deck Hemi 1871 DMPE Roots making 48 lbs for years, 2800 lbs 10.5 Truck runs low 4.teens. at 180mph 1.30 first gear 2 speed trans. I like to keep it at 9000 rpm and its always been easy on parts.

    Question: Will a 4.15 stroke with a 4.46 bore 526ci make more power everything else above kept the same including 9000 max rpm????

    Keeping in mine its a heavy race truck and I will keep it at 9000 rpm's wiill the shorter stroke require more RPM to make the power., or at my relatively low rpm favor the 4.375 Also with the 1.30 first gear Im in first gear for a long time I shift at 9000 and it cross the 1/8 stripe at 9000 ish


    I need a new crank and trying to decide thanks ITA
     
    #1
    moparchris440, Dec 2, 2016
  2. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    The biggest gain you will see will not be from stroke - it will be from the bigger bore. It will unshroud the valves allowing for better flow. You will probably be able to run about a degree more timing than you would with the 4.375 bore.

    If you are on a budget (aren't we all) any time you can get away with a shorter stroke, it's easier on parts. The load on the big end of the rod and the rod bolts goes up exponentially with stroke.

    You may lose some low end torque by reducing the stroke.

    I don't know what you have for valve train parts, but a late model hemi like you have don't care one damn bit about going 9500. Your valve springs may go from lasting 100 runs to like 90 runs but you see what I'm getting at. Especially if you drop the stroke. If you had some old fuel heads or a big chamber Veney, 9000 is a good limit. If you came from Chebby's I know 9000 might as well be 14,000. But the parts you are running were designed to work at 10,000+.
     
    #2
    Will Hanna, Dec 5, 2016
  3. jay70cuda

    jay70cuda Well-Known Member

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    Unshrouding the valve is the biggest thing you'll gain. That's why you see guys now running a 3.900 crank and 4.500 bore. The new hemi has massive sleeves in it allowing for great airflow. Rev it up. 9000 isn't even stretching her legs yet...
     
    #3
    jay70cuda, Dec 5, 2016
    Will Hanna likes this.

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