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Thread: Motor choice-

  1. #11

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    Barry runs a fuel injected BBC in a street legal mud truck. Stop overthinking the event. BBC has more torque. More Torque = better mileage, more trail grunt, and it's not a 350.

    Once I put that stuff on a pallet...no backing out!
    Big Blocks RULE!

  2. #12

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    Tom,

    I have alerted the wife to my plans and started amassing things for the ebay. I hope to have your money in 2 weeks as opposed to the month I requested. Jean Ellen is currently e-mailing you about how to suprise me with the purchase of the front locker.

    I am not worried about the BB, but the gears do worry me. I may just hold those until I get more guts.
    -B.

  3. #13
    Join Date
    Sep 1998
    Location
    Winlock, WA
    Posts
    2,553

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    Big block = more rotating mass (more kenetic energy).
    Small block = less rotating mass (more efficient).
    Cause I can find a 352, or a 383 big block, and a 400 small block.
    Diesel, especially with a turbo Cummins, figure that the torque is roughly twice that of the HP. Much more efficient use of the fuel, and the fuel itself contains more energy (BTU's per lb of fuel).

    Now, the big advantage of the big block over the other two is that our truck isn't really that light weight. So you have to have the better gears to have enough mechanical advantage to use the small block. The diesel can use lower gears and bigger tires, get great mileage, and has tons of torque in the lower power band.
    Big block, you can still rev them up to a decent RPM if need by. You can't do this in a diesel. And if you are in the wrong gear, you have enough power to power through it, where most small blocks can't do this.

    Of course, add a supercharger or turbo, and you change the entire equation.

  4. #14
    Join Date
    Dec 2003
    Location
    West-central Ohio
    Posts
    689

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    Sorry, Dave, but torque is more a function of stroke. Envision the crankshaft with the piston an the center of travel - the crank throw is horizontal. The longer the stroke, the farther away from crank centerline (fulcrum) the force is applied. Jsut like slipping a "cheater bar" pipe over a braker bar to gain leverage, the longer stroke provides more leverage against the crankshaft. Piston diamerter DOES play a role, of course but that of displacement along with stroke length.

    The old conventinal wisdom stated that a "square" engine (one inwhich the stroke = bore) was a good all-around engine. An under square engine (bore < stroke) made a good torquer, and an oversquare engine (bore > stroke) made a good hi-revver (like the venerable Dodge 340). For an application with 5.87's, torque is not a big concern (breaking parts with too much is, however), but an angine capable of fast spin-up and sustained hi-rpm would be MY preference.

    A 283 chebbie (3.875" bore/3" stroke) or 340 Mopar (4.04" bore/ 3.31" stroke) (note capitalizations? heh heh heh!) would SCREAM!

    Go here to see other combinations:
    http://www.zccw.org/Tech/Engine/06-97LongShort.html

    To the torque crowd, I'dlike to see a 'binder engine swapped in!

    But that's just me...

    Bob
    "other peoples junk, is something or other" - Militarypotts 02/07/2011

  5. #15
    Join Date
    Dec 2003
    Location
    Lone Pine, CA
    Posts
    451

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    Brian, here's my opinion...

    With stock gears I'd stick with a small block. First off for it's shorter stroke and lighter everything it's more suited to higher rpms. Plus with the gearing stock to our trucks, you'll have more than enough power to do most anything except full on boggin' but that's a moot point as 5.87's are a bit deep in my opinion for mud, same with sand.

    As far as gaining mileage, that's a moot point too unless you spend most of your driving time at low speeds. Ideally you want to gear the axles to meet the torque curve for most conditions. With our deepass gears you jump way over that curve in all but the very specialized engines. So at freeway rpms you're too high in the revs to notice much difference either way.

    Chris

  6. #16

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    5.87's are a bit deep for just about anything-- lots of rock crawlers here running 4.89's or so, w/low t-cases or something. Why? Because too low a gear in the axle doesn't let them roll fast enough to get out of their own way going down steep rock faces, and that's not good. Anyway.

    Brian: Torque is king. Big blocks have more. That's it!
    **I heart Bump_r **

  7. #17
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,520

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    Following up on Bump's oversquare scenario....400 BB Dodge, 4.342 bore by 3.38 stroke....oversquare to beat the band, with some 2.08 intake valves that can go up to 2.14 right now.
    Being this is big block, but the stroke is so short, it isnt a torque motor in fact is has less stroke than a 350 chevy but wil rap up faster and make more horsepower without question...comparably built of course. With 5.87 gears and especially with double tcases or other underdrive units, this motor seems to be perfect for the M715 on road and off...plenty of power for 60-70 mph cruising and not to much torque to split axle shafts like twigs off road.
    My opinion, but makes sense to me!
    brute4c
    Lord send your Holy Ghost into our hearts and make the desire of our hearts Your Will.

    Pro-choice, that's a LIE, babies don't choose to die!!

  8. #18

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    Thanks you guys for enlightening me.
    Basically what I learned is that with the stock gears a 350 would be perfect sicne I'd want the higher rever and not need a torque monster due to the gears and torque multiplications.

    With a bb, I'd need the higher gears to keep from overrevving and also to keep from twisting shafts due to more torque output.

    So, right now my setup is good, and in a year when I swap in the 366 and the 4.56's my setup will be just as good.

    Bump- thanks for giving me the reason why all this happens. Before it was just talk, but you backed it up with math.
    Brute- Glad you're back around. We missed you.

    -B.

  9. #19

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    Thanks Bump for puting up the link to that article- makes for interesting reading. I've read similar articles on the Speed-o-motive website, that was awhile back and I don't have their address handy or I'd reference it. Maybe later I'll dig it up again. All these opinions are some good food for thought.

  10. #20

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    WHAT THE F*$K?!! That table is cracked out! I can appreciate the math done, but ...it's speculation on stuff nobody does!! NOBODY built 283's with 6.5" rods.

    Since I'm not up on ford or Mopar lengths, let me just give a quick real world Spiceresque nutshell on chevy.

    5.7" rod length from 262 to 350 V8's. 6.0" is the next best length step for the buck and 6.100", 6.125" and 6.200" are high buck Nascar lenghts for wicked high revs and great rod ratios.

    400's use 5.565" stock rod. A switch to 5.7" rods is nice and frees up some revs and is quite common. 6.0" rod gets you into wicked expensive pistons, along with possible cam clearance issues and the need to possible switch to a small base circle cam or clearanced rods.

    There IS NO 400 factory Big block. 396 or 402 not 400. 400 is sbc.

    Big blocks from 366 and 427TD and 396-502 all run 6.135" rods stock.
    6.385", 6.535", 6.600" (a sweet Bill Miller length) and 6.800" are the most popular flat out high rev rat rods.
    Big Blocks RULE!

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