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SBC what RPM range is ok for highway use?

Discussion in 'The Hokey Ass Message Board' started by lotus, Feb 25, 2010.

  1. lotus
    Joined:
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    lotus Member

    What is an acceptable RPM range for a SBC at highway speed?

    I have a 383 SBC with 700R4 tranny, 4.56 posi, and 28" tall tires...here is what I am looking at with that setup.

    RPM:2500
    Tire Diameter: 28"
    Axle Ratio 4.56
    Transmission Ratio: .7
    MPH = 65.27

    This is going to be in a 55 chev truck.

    2500RPM seems like it would not shorten the life of t he motor and be doable on 2hour trips to the coast.

    just realized to...when it drops out of OD 65mph becomes 3700 RPM

    what do you think?


  2. Frank K
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    Frank K Member

    Safe for cross country...Frank Kunkel
  3. Desoto291Hemi
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    Desoto291Hemi Member

    Sounds good,,it should work fine.
    In overdrive,,I would prefer a little bit less rpm at highway speeds,,,around 2200,,but it won't hurt a thing.
    The 4.56 gear should really haul when it is needed.

    Tommy
  4. GREASEMONKEY72
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    GREASEMONKEY72 Member

    2500 aint bad at all
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  5. lotus
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    lotus Member

    yeah i figure it will be a blast to drive around town...should be a stump puller and still be drivable on the highway. The motor should make most of its torque/hp under 5k rpm.

    i imagine i will be spending time working on getting it to hook up vs hop really bad.
  6. big creep
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    big creep Member

    yea that sounds about right. my work truck runs a little closer to 2200 rpms and thats with 4.11 in the back.
  7. 3wLarry
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    3wLarry Member

    I got a 3:55 rear gear in my '56 chevy truck and a crate motor 350/350 trans...it does 70 mph all day long at 2800 rpm's. Doesn't get great gas mileage, but who cares?
  8. Diehard32
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    Diehard32 Member

    Depends on how fast you want to get where your going.... Just kiddin':D

    With that stump puller gear, your mileage will suffer somewhat, but it all depends on how far you plan to travel.
    Longer trips = mo $$$......But its just money.
  9. lotus
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    lotus Member

    yeah i am not too concerned with gas mileage...I also have a Ford 8.8 with 3.73 gears that I will put in if I decide the 10bolt 4.56 is too much.

    avg trips will be 2 hour trips to the coast/LA. longest trip it would see could be Vegas from Bako or to the Bay area...
  10. hotroddon
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    hotroddon Member

    Back in the days before Overdrive transmissions, we used to figure a 40% rule for highway driving a "real" Hot Rod. In other words 2400 at 60mph 2800 at 70 etc. Still gave strong acceleration and was livable on the road.

    I used to drive a 331" small block from So Cal to Northern Cal and Vegas regularly at 2800-3000 rpm, and other than using a bit of gas, no big deal. Put a ton of miles on it
  11. Lalos53Ford
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    Lalos53Ford Member

    I run around 2600 rpm at 70 mph on the highway and seems to be just fine. She has plenty left when I gas on her. 355/th350 does nice.
  12. hotrod40coupe
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    hotrod40coupe
    ALLIANCE MEMBER

    Like everyone has said, shouldn't be a problem as long as you are willing to sacrafice mileage.
  13. J&JHotrods
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    J&JHotrods Member

    Sounds like the passing gear will be in the meat of the power range. Not the best for MPG, but ought to be fun!
  14. Truckedup
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    Truckedup Member

    A lot of guys,me included, used to run 4-1/2's and gave no thought to buzzing down the hiway at 3500 rpm for hours.Not only SBC's but BBC's and B block Mopars.
  15. 53vicky
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    53vicky Member

    I drove my 283 with a 2 speed powergluide from nor cal to so cal all the way at probably 3500 rpms. Didnt seem to hurt her at all.
    It actually was good my my tranny to run it for awhile like that.
  16. ChevyRat
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    ChevyRat Member

    Does not sound to bad at all
  17. cleatus
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    cleatus Member

    I think the 4.56 gears will be way overkill, unless you are running some really wide rubber.
    I also have a 383/700R4 and my gears are only 3.25.
    Granted, my 3.25 are actually overkill in the opposite direction - 3.50 would be more ideal, but even with the 3.25 gears I can easily spin both rears off the line, so how much more bottom end grunt is really needed?
    And it is really nice to hit the Interstate at 1900 rpm.
    4.11 would still be more than good.
  18. mustang9093
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    mustang9093 Member

    Good combo with a killer first gear. Make shure the camshaft is happy at highway rpm. Drag race cams and overdrives dont get along.
  19. Russco
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    Russco Member

    Thats a final drive ratio of 3.19 which is very close to the 3.08 millions of SBC came from the factory with it will do more than that easily alll day long
  20. lotus
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    lotus Member

    the 28" tall wheels i have right now will not hook up at all... 235x70x15

    I am still debating on running steel wheels with cheater slicks in the back or running my rocket wheels with some meaty tires in the back.

    I ended up with the 4.56 10bolt because it was a hell of a deal and has after market axles...ideally i would like something a little less dramatic but i am going to run it and see how I like it before I make any changes.
  21. oldspert
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    oldspert Member

    I drove a 61 Vette with 283 from central Texas to Meade Kansas running a 4:11 and four speed. Tacked around 3800-3900 all the way. Temp was around 95 in summertime. No problems at all except for getting 8MPG.
  22. detroitiron
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    detroitiron Member

    My '92 Explorer w/V6 Auto in overdrive is 2500 @ 65 mph. It has almost 187,000 miles.

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