is this a safe and correct bore size?

Discussion in 'Blocks' started by Grumpy, Sep 22, 2018.

  1. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member





    displacement is calculated with this formula
    bore x bore x stroke x # cylinders X .7854= displacement

    4.04 x 4.04 x 3.48 x 8=356.8

    yeah, .040 over is a common and rather safe over bore diam,
    pull out your feeler gauge and look at the .020
    gauge, they took that much bore wall out on both sides,

    [​IMG]

    I would not be overly concerned.....
    hundreds of thousands of 327-350 engines have been rebuilt safely with a .030-.040 and even a .060 over bore,
    (.060) over bore on the stock OEM block is considered the safe max
    its always best to have a block sonic checked before its bored.
    .060 over bore is generally considered a semi safe over bore,
    but its always best to have a block sonic tested at and bore size over .040,
    just too be certain core shift is not an issue.
    aftermarket blocks like DART sells are considerably stronger,
    and have both thicker castings and a better alloy,
    making them a far better performance option once you push the, sbc
    hp north of 450 hp.




    Chevy V8 bore & stroke chart

    I saw this online and figured I would post it..I am going to add the popular lsx strokers soon
    CID BORE STROKE
    262 = 3.671" x 3.10" (Gen. I, 5.7" rod)
    265 = 3.750" x 3.00" ('55-'57 Gen.I, 5.7" rod)
    265 = 3.750" x 3.00" ('94-'96 Gen.II, 4.3 liter V-8 "L99", 5.94" rod)
    267 = 3.500" x 3.48" (Gen.I, 5.7" rod)
    283 = 3.875" x 3.00" (Gen.I, 5.7" rod)
    293 = 3.779" x 3.27" ('99-later, Gen.III, "LR4" 4.8 Liter Vortec, 6.278" rod)
    302 = 4.000" x 3.00" (Gen.I, 5.7" rod)
    305 = 3.736" x 3.48" (Gen.I, 5.7" rod)
    307 = 3.875" x 3.25" (Gen.I, 5.7" rod)
    325 = 3.779" x 3.622" ('99-later, Gen.III, "LM7", "LS4 front wheel drive V-8" 5.3 Liter Vortec, 6.098" rod)
    327 = 4.000" x 3.25" (Gen.I, 5.7" rod)
    345 = 3.893" x 3.622" ('97-later, Gen.III, "LS1", 6.098" rod)
    350 = 4.000" x 3.48" (Gen.I, 5.7" rod)
    350 = 4.000" x 3.48" ('96-'01, Gen. I, Vortec, 5.7" rod)
    350 = 3.900" x 3.66" ('89-'95, "LT5", in "ZR1" Corvette 32-valve DOHC, 5.74" rod)
    364 = 4.000" x 3.622" ('99-later, Gen.III, "LS2", "LQ4" 6.0 Liter Vortec, 6.098" rod)
    376 = 4.065" x 3.622" (2007-later, Gen. IV, "L92", Cadillac Escalade, GMC Yukon)
    383 = 4.000" x 3.80" ('00, "HT 383", Gen.I truck crate motor, 5.7" rod)
    400 = 4.125" x 3.75" (Gen.I, 5.565" rod)
    427 = 4.125" x 4.00" (2006 Gen.IV, LS7 SBC, titanium rods)

    Two common, non-factory small block combinations:

    377 = 4.155" x 3.48" (5.7" or 6.00" rod)
    400 block and a 350 crank with "spacer" main bearings
    383 = 4.030" x 3.75" (5.565" or 5.7" or 6.0" rod)
    350 block and a 400 crank, main bearing crank journals
    cut to 350 size

    ALL production big blocks used a 6.135" length rod.
    CHEVY BIG BLOCK V-8 BORE AND STROKE


    366T = 3.935" x 3.76"
    396 = 4.096" x 3.76"
    402 = 4.125" x 3.76"
    427 = 4.250" x 3.76"
    427T = 4.250" x 3.76"
    454 = 4.250" x 4.00"
    477= 4.5" bore x 3.76" stroke
    496 = 4.250" x 4.37" (2001 Vortec 8100, 8.1 liter)
    502 = 4.466" x 4.00"
    557T= 4.5 bore 4.375" stroke
    572T = 4.560" x 4.375" (2003 "ZZ572" crate motors)

    T = Tall Deck
    always accurately measure the crank main journals,
    and remember the crank and block bearing sizes on a 400 sbc and 350 sbc,
    are different as are the early 283-327 sbc



    ID also point out, that before you buy any engine in an unknown condition,

    https://www.jegs.com/i/Blueprint-Engines/138/BP3830CT1/10002/-1

    https://www.jegs.com/i/Chevrolet-Performance/809/19355658/10002/-1

    https://www.summitracing.com/parts/mll-bp3501ctc1

    https://blueprintengines.com/collec...s/gm-350-with-vortec-heads-roller-cam-1pc-rms

    you have the option of new rebuilt professionally assembled engines, and you don,t have to wonder the condition, or if it will run and in some cases a warranty

    related info

    http://garage.grumpysperformance.co...onnecting-rod-rod-length-too-stroke-info.510/

    http://garage.grumpysperformance.com/index.php?threads/engine-block-cylinder-wall-thickness.976/

    http://garage.grumpysperformance.co...-potential-dream-bbc-combos.14607/#post-77976

    http://garage.grumpysperformance.co...on-ring-info-youll-need.509/page-2#post-77510

    http://garage.grumpysperformance.com/index.php?threads/oil-system-mods-that-help.2187/

    http://garage.grumpysperformance.co...alves-and-polishing-combustion-chambers.2630/

    http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/
     
    Last edited: Sep 23, 2018
  2. busterrm

    busterrm solid fixture here in the forum

    They say in docs that dart block can go 4.165, but my machine shop says they capable of a 4.185 bore and still be safe. Jimmy says he has sonic tested many dart shp blocks and he might even trust 4.195 with a good casting.
     

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