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Thread: Top speed with a small block chevy?

  1. #1

    Default Top speed with a small block chevy?

    Hello, Allow me to introduce myself, My name is Curtis Newman, and after years of looking, I finally found an m-715 that is close to home and in my price range, so after wiping off some drewl I got out the check-book and drove home my new 1967 m-715
    yesterday(man it was sweet), It is all stock, with a top speed is 45mph, and I am wondering what the top speed of a slightly modified 350 chevy powered m-715 is?

  2. #2
    Join Date
    Feb 2004
    Location
    Silver Lake Sand Dunes MI
    Posts
    1,490

    Default

    With stock gearing and size tires you will still only run 55-60. Which is what a good running 230 should do. 45 means that you motor just need a tune up to get the best out of it. A search here should turn up plenty of tune up tips. The big limiting factor in speed is the stock 5:83 gearing. If you want to run hiway speeds then start looking to regear the axles, or switch to a larger tire.

    Dave
    1967 Kaiser Jeep M715 weapons carrier:http://www.davidallenracing.com/M715.htm
    1967 Kaiser Jeep M35a2 2.5 ton cargo truck: http://www.davidallenracing.com/M35A2.htm
    Delta Team Decals: http://www.i2k.com/~schwarzd/

  3. #3
    Join Date
    Dec 2006
    Location
    KINGSPORT, TN.
    Posts
    229

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    45 is wide open, yes it will go faster but if you want it to live 45 max JMO

  4. #4
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,520

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    If the truck is one of the later models with the governor under the carb, 45 may be about all one can do without removing that.

    It should be able to do 60 MPH, but it is at a fairly high rpm for the stock engine, close to 3500 RPM's, which isnt a good constant speed in most cases. The transfer cases also have penchant for developing super high temperatures that lead to seal and lube failure....the latter ruining the case. For any kind of distance driving, more than 30-40 miles of fairly flat ground at speed, 50 MPH has been shown to be a reasonable speed lmit to self impose on the system. More than that, or even trying to maintain that in steep terrain, leads to high heat and problems in the t-case.
    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!!

  5. #5
    Join Date
    Dec 2003
    Location
    parsons Kansas
    Posts
    476

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    with the 725 and all stock drivetrain, with a 350 and 38.5 boggers, I had an emergency and it was taching 6000 all the way home (13 miles) to get my step daughter to the hospital and by the formulas, I was close to 100 mph.
    nothing was found out then but later we found that she had heart problems with the valves, needs a regrind job.
    on the highway I can keep up with traffic but not recommended as about 3500 rpms is hard on the engine and it wont live long. the low gears work real good offroad as most people try to regear there trucks to be as low as our are stock.

  6. #6
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,520

    Default

    IF....you change out the stock tcase for an NP205 and have a decent running 350, you could run 60 as long as you like....course you still would be pushing 3500 RPM's on a contant basis and over time, thats not the kindest thing for such a motor. The NP205 will not have the heat problems of the stock NP200...so much the better...

    You can go to a 38 inch tall tire without doing any suspension mods or lifting the truck...drops the 60 MPH rpm from 3482, with the stock 34 inch tires, to 3115...a bit easier on the motor and the gas pump....

    Up to you then how much you want to push it....
    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!!

  7. #7
    Join Date
    Mar 2004
    Location
    northern Arizona
    Posts
    1,025

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    I generally run my 725 right around 3000 rpm with 36" tires - I'm told that's around 54-55 mph, fast enough pushing a barn.

  8. #8

    Default

    Budget allowing, I prefer to stick to the stock configuration. 45 mph is fine
    for now; But I do have a spare small block in my other truck, worst case I will drop it in, until then it will be 45mph.

  9. #9
    Join Date
    Oct 2006
    Location
    Atlanta, Ga.
    Posts
    369

    Default

    With a 383, TH400 tranny, an NP203/205 Doubler, 4.56 gears, and 38.5" tires, my truck cruises very well at 60-65... I've had it to a top speed of 75-80 a couple of times, but that's more excitement than I need in a day's fun...

  10. #10
    Join Date
    Oct 2006
    Location
    Atlanta, Ga.
    Posts
    369

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    one other item here... If you DID stick with a stock driveline, the NP200 would be your limiting factor. All other things being equal, it won't live too long above 45MPH.

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