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454 Piston differences in the same motor...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mountainexplorer, Sep 23, 2003.

  1. mountainexplorer

    mountainexplorer 1/2 ton status

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    Just got this '73 454 motor. Pulled the heads off. Its standard bore with hardly any ridge. Looks like someone had replaced rings and bearings before, and replaced one piston.

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    Now, isnt the mis-matched piston a flat-top? and the others are dished... so, this can't be good to run, can it? I dont think the two larger valve reliefs are enough on the flat-top to compensate for the dish in the others.
     
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Yeah, that isn't correct. I have seen an engine that was never apart before have 1 different piston in it from the factory. Compression would be different between that cylinder and all the others. Take that piston out and look on the inside of it to so see if there is a GM number in it, I think the number will be about 6 or 7 characters long and usually starting with a 3. Sometimes you will even find that the piston will say GM on the outside edge of it also if it were a factory piston. Regardless, look at the other 7 pistons and take the number from the inside of one of them and purchase a match to it.
     
  3. bablazer73

    bablazer73 1/2 ton status

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    I have seen(and been asked too) replace 1 damaged piston because people are to cheap to fix an engine right! Some cheapo parts people sell "generic" O.E. pistons and the only list 1 style(the most common) as a replacement for ALL the engines! I hope your gonna fix it!
     
  4. R72K5

    R72K5 Banned

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    i wouldmeasure CC's of the reliefs in both styles of pistons, they might be same or close, those are both some wierd looking piston designs, which- if either- are stock ?
    keep in mind theres two stock designs, depending on head chamber volume.
     
  5. Mudzer

    Mudzer 1/2 ton status Author

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    I wouldn't be as concerned by the piston relief volume as I would be the weight of the piston. Of course, if they are same weight, then I would be concerned about the relief - if that makes sense. You can get a serious vibration in the engine and bearing failure with mis matched pistions.
     

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