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Crusing Speed RPM

Discussion in 'The Garage' started by CHEVY 4WD, Dec 9, 2002.

  1. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    Whats a safe crusing RPM for long distances in a SBC?
     
  2. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    well with my 3.73s and 36"s i run about 2200 at 65. but i'm going to 4.56s soon which will put me at about 2800 i think.
     
  3. Shaggy

    Shaggy 3/4 ton status

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    <font color="green"> Anywhere between 2200-2800 is fine. Even as high as 3000 should be OK. Maximum effeciency, IIRC, is around 2400. Lower than 2200 it might bog a bit when you pass. </font color>
     
  4. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    </font><blockquote><font class="small">In reply to:</font><hr />
    Lower than 2200 it might bog a bit when you pass.

    [/ QUOTE ] it does /forums/images/graemlins/frown.gif
     
  5. 87sm465np208

    87sm465np208 1/2 ton status

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    my cruiseing speed with my 1:1 ratio in the 465 and the 3.08 gears puts me at about 2K rpm at 55mph, so yea OD does help on those long trips, unless yur pulling a heavy trailer. /forums/images/graemlins/thumb.gif

    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/truck.gif
     
  6. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    I found 2200 to be perfect for me. With my 31's and 4.10 gears (was cheating, I have a 700r4), I cruised about 2200 at 70. Now that I'm getting 36's, I wish I'd gone 4.88.
     
  7. POWERMAD

    POWERMAD 1/2 ton status

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    I drive my rig 100 miles a day and most is freeway traffic.
    I turn 3K and am doing about 70.
    Been driving that for over a year now.
    lil ol 305 too. but she is starting to poop out.
     
  8. MilpitasK5

    MilpitasK5 1/2 ton status

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    So would it be safe to say that 1600-1700 in OD is bad for my junk? I've have had this coversation with others and haven't used OD since.
     
  9. GMslave

    GMslave 1/2 ton status

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    Whoa, hold on!! You said </font><blockquote><font class="small">In reply to:</font><hr />
    I turn 3K and am doing about 70.


    [/ QUOTE ] Are you sure? Cuz I turn 3000 at 70 mph (as per GPS and Autometer) but I'm on 35's. Your bio sez you're on 33's with 4:10's, has that changed? I assumed I had 4:10's in my 77 3/4 ton, but that doesn't seem to make sennse. Did the factory offer 4:56 stock? /forums/images/graemlins/confused.gif I've never had the covers off of it, and now it's freezing outside. Does this seem right to anybody?
     
  10. POWERMAD

    POWERMAD 1/2 ton status

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    According to all the calculators that is what I am doing.
    My speedo crapped out on me awhile ago so I just use the tach.
    My tires are actualy 31" tall so at 70 with 4:10's I am turning about 3K
     
  11. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    I ran my 383 a lot around 3K rpm since with 3.73's my overdrive wasn't much use. I didn't have the best motor longevity, I had cam bearings crap on me and the piston fit isn't that great anymore. This is within about 100K miles over the span of about 7 years and I wasn't exactly gentle with it. I ran some pretty big passes on a regular basis as fast as the truck would go. It is a short rod setup.

    In my 'burb with the 4.56's and 315/75's in OD it runs OK but could still use more power. I figure I'm doing 2250 to 2300 rpm and more wouldn't hurt. 4.88's or 33" tires would do the trick I think, or adding some more power. I have a stock EFI 350 in the 'burb.
     

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