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Losing engine power?

Discussion in 'Rocky Mountain Region' started by nau81blazer, Apr 6, 2005.

  1. nau81blazer

    nau81blazer 1/2 ton status

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    Hey guys,

    Well, whenever I drive the Blazer down from Flagstaff to Phoenix i have to go up the hill out of Verde Valley. Anyway, whenever I'm on the hill the truck will start out fine and then just lose all of "go" about half way up. It's not heating up at all and I'm really not railing on it that hard (3k rpm). What could cause this. It has a 350 and 2.73 gear with 33's. No, that's not a miss print 2.73 gears. That still doesn't explain why it would dog so much. By the time i'm near the top i'm getting passed by Semi's going like 30mph. Any ideas? Thanks for the input!

    --Adam
     
  2. Hossbaby50

    Hossbaby50 3/4 ton status

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    You may have a plugged up catylitic converter. My truck did that a couple times when the cats would be going out. Might have it checked out.

    Harley
     
  3. marv_springer

    marv_springer 1/2 ton status

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    Adam,

    Remember that you're gaining some pretty significant elevation on that hill. Just because the air gets thinner, power levels are prolly 15% (just a guess.....:dunno: ) less at the top than at the bottom.

    small block motor w/ 2.73's and 33's is not geared for hill climbing.

    Maybe you do really have an engine malfunction..... I'm saying just consider the possibility that you don't.

    Marv
     
  4. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    My truck would do that with 31's and 3.08's every time I went up a grade like that in 2wd . I concur with Marv .

    By way of comparision , I went to 33's with 3.73's , and while not as low as I would of liked , or what was reccomended . It does run a ton better . On the highway on light grades I can keep it in OD , on steeper grades it uses 3rd , and very rarely do I need 2nd gear anymore .
     
  5. nau81blazer

    nau81blazer 1/2 ton status

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    Cool,

    Thanks for the input guys. I realize that 33's and 2.73's are not a good highway combo, but it'll have to do for now. I was just wondering if that was something you've ever heard of engine problem wise, guess it's just the nature of the set up though. Also if i really get it up in the RPM's it starts to smoke. Bad piston rings? This summer it's engine rebuild/new engine time so until then i'll deal with it I guess. Thanks again for the input guys.

    --Adam
     
  6. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    What color is the smoke ? We can all guess after we know that . Bluish , white , black . They all indicate different things . Motor is probably tired if its original . My friend Tj's rig smokes a bunch , it has over 225,000 miles on it , yet his truck pulls pretty good with the 4.10's and 33's and injection .
     
  7. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Also, loosing power at higher altitudes comes in two "flavors" which are closely related but can be dealt with separately. One is simply due to lower atmospheric pressure reducing the efficiency of the engine and can only be "corrected" (in relation to sea level power output) with forced induction (turbo or supercharger). The other is related to lower oxygen content by volume causing it to run rich if not properly jetted for higher altitude driving. If your carbed vehicle is jetted for the altitude it does not loose nearly as much power (relative to sea level), but it then runs lean when driving at lower altitudes. Lean is much more likely to cause problems so carbs are often set up a bit on the rich side even at higher altitudes.

    IMO, this is one of the biggest reasons to run *closed loop* EFI in a multi-purpose vehicle in areas like this (around the Rockies or other similar terrain). There are a whole other set of additional benefits to using EFI both on and off road, but dealing with altitude changes, particularly if you do something like go from Flagstaff to Phoenix on a regular basis, is a HUGE plus that makes the upgrade worthwhile all on it's own. And adding closed loop TBI is not difficult or expensive, particularly relative to the benefit over carbed performance in this case. Obviously forced induction on a gas V8 is a bit more involved and probably not worth looking into in most cases.

    Take that with a grain of salt, but it is my understanding though I am FAR from a carburetion tuning and efficiency expert. We have some carb wizards around here who can correct or add details as needed.
     

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