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454 problems

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 75blazer454, Oct 15, 2002.

  1. 75blazer454

    75blazer454 Registered Member

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    i cant get my 454 over 4000 rpm.. and i have a lot more power to give it!
    some ideas??

    sorry for my bad english /forums/images/graemlins/smile.gif
     
  2. POWERMAD

    POWERMAD 1/2 ton status

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    What are your tire and gear ratio combination?
    What are the specs of the engine?
    Is there a rev limiter on the ignition?
    A few more details help out, that and filling out your profile.
    Does it rev higher than 4000 with it in park or just when you are driving down the road?
    .
    BTW welcome to CK5. /forums/images/graemlins/pimp1.gif
     
  3. 75blazer454

    75blazer454 Registered Member

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    i have 33" and 3.08? or 3.80? its a original 12 bolt for the 75 mod.

    i do not now the specs on the motor, but it have a Holley 850 cfm 4150 mod i think. and a weiland 1800 under the holley. and rusty old headers. its a 73mod enegine, it has around 400hp but i dont now whats inside it.

    when its in park i can get it higher but it starts to backfiere (sounds like explosives in the exaust.) the same thing hapens when i am driving. i dont have a rev limiter.

    bad english i now! /forums/images/graemlins/smile.gif
     
  4. POWERMAD

    POWERMAD 1/2 ton status

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    Did you just give it a tune up?
    Or did this just start happening.
    Kinda sounds like ya have crosssed plug wires.
     
  5. Sandman

    Sandman 3/4 ton status Author

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    Might be some kind of timing problem. Check the timing and maybe even pop the cap and check the rotor. And checking the wires like he said is a real good idea.
     
  6. 75blazer454

    75blazer454 Registered Member

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    i have had a "small" tune up, but no help.
    all the ignition parts are new... rotor and cap are good.
    new exspensive plug wires, i dont think they are in the wrong positions but i am going to check it out.

    Kristoffer /forums/images/graemlins/k5.gif /forums/images/graemlins/cool.gif
     
  7. 75blazer454

    75blazer454 Registered Member

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    hmmm. if i have spark plugs thats made for 80mod in my 73mod enegine, can that be my problem? /forums/images/graemlins/ears.gif
    i dont have HEI.

    ?????
     
  8. Z3PR

    Z3PR Banned

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    I'd consitter a gear swap. I too have 307's or 308's or whatever in my stock 76 axles. I'm doing a axle swap in the near future. The 78 3/4 ton axles I'm swaping in have 373 gears Better then the current gears, but I'm also going to 35" tires. Hope it'll be okay till I can aford to get 456 gears.
     
  9. 75blazer454

    75blazer454 Registered Member

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    all my plug wires is where they shoud be.

    sorry for my bad english
    kristoffer
     
  10. POWERMAD

    POWERMAD 1/2 ton status

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    This was happening before the tune up?
    I am going to assume that the wires and ignition is fine.
    A couple of things come to mind.
    one is the timing chain may be worn out.
    or cam with a flat lobe would also do as you are describing.
    Big Blocks have a bad rep for being cam eaters.
    pull off the valve covers and check to see if any of the springs are broken, then disable the coil and have someone crank the engine over and see if the rocker arms are moving about the same.
    Usualy when a lobe goes flat you will have a clattering valve.
    To check for a worn timing chain remove the distributor cap and turn the crank by hand one way and then the next.
    if the crank moves quite a bit in both directions and the rotor is not moving then that is an indication of the chain being worn out.
     

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