4.6 N* Cylinder walls
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Northstar Engines and System Technical Discussion Discussion, 4.6 N* Cylinder walls in Cadillac Engine Technical Discussion; Just started a N* rebuild and after removing the heads noticed some blued areas in a couple of cylinders Likely ...
  1. #1
    tero is offline Cadillac Owners Member
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    4.6 N* Cylinder walls

    Just started a N* rebuild and after removing the heads noticed some blued areas in a couple of cylinders
    Likely caused by overheating due to faulty HG. What do you think should i ditch the block?

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    stoveguyy is offline Cadillac Owners Connoisseur
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    Did u buy car to fix or was it yours to begin with so you have some history? Sounds like you don't know how much car was abused?

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, slap in a big stereo
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    Re: 4.6 N* Cylinder walls

    A cylinder block overheat would be about 1,100 degrees too cold to 'blue' a cylinder wall. The head gasket failure was due to head bolts pulling from the compromised cylinder block bolt holes. That's why you need to insert or stud all 20 bolt holes.

    If the original cylinder wall cross hatching is still evident, clean the cylinders thoroughly with lacquer thinner, apply a coat of synthetic engine oil and install a new set of rings spec'd for the engine. These engines almost never need honing and almost never leave a step at the top of the piston ring travel - check it out with a fingernail scraped up the cylinder walls. Be dead SURE to install the new ring set according to instructions - including the second compression ring: dot up.

    Study the GM service manual concerning cylinder walls, wall finish, why not to hone, engine overhaul and other such mundane Northstar stuff. A good check of the cylinder roundness and taper will tell you whether the block is serviceable.

    Read through the sticky posts just above these recent threads - ^^^ . Study the Cadillac Technical Archive way up ^^^ in the top black bar.

  5. #4
    JoeTahoe is offline Cadillac Owners Fanatic
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    Can you get some pictures and show the blue areas
    maeng9981 likes this.

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    Re: 4.6 N* Cylinder walls

    Quote Originally Posted by Submariner409 View Post
    A cylinder block overheat would be about 1,100 degrees too cold to 'blue' a cylinder wall.


    If the original cylinder wall cross hatching is still evident,
    Here's what they should look like. At 130K & 170 K
    Attached Images

  7. #6
    tero is offline Cadillac Owners Member
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    Re: 4.6 N* Cylinder walls

    sorry that it's taken this long.....busy busy busy

    i just don't like the looks of this cylinder wall
    DSCN0704.JPG

    i've even gone so far as to get a complete second block


    This is what i know of these two engines. The original has 53k with hg problems, likely drove hard.
    Probably the cause of the burnt cylinder wall.
    Was running when i tore it down.

    the second had roughly the same mileage but was burning excessive amounts of oil.
    i popped out one piston DSCN0705.JPG
    bearing looked decent obviously carboned build up with sticky rings

    i haven't done any measuring yet

    just trying to decide which one to work on.

  8. #7
    stoveguyy is offline Cadillac Owners Connoisseur
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    Are there bolt threads near surface in closer holes and no threads visible in rear bolt holes?

  9. #8
    tero is offline Cadillac Owners Member
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    Re: 4.6 N* Cylinder walls

    i drilled and tapped a few holes in the first block for studs
    before noticing cylinder walls

  10. #9
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    Re: 4.6 N* Cylinder walls

    Quote Originally Posted by tero View Post
    This is what i know of these two engines. The original has 53k with hg problems, likely drove hard.
    As it was intended to be.


    Probably the cause of the burnt cylinder wall.
    Not likely

  11. #10
    stoveguyy is offline Cadillac Owners Connoisseur
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    Re: 4.6 N* Cylinder walls

    assume 2nd block has pistons/rods? are you going to rering 2nd motor? bearings?

  12. #11
    tero is offline Cadillac Owners Member
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    Re: 4.6 N* Cylinder walls

    i just like the looks of the second motor
    it came apart so much better. Even the head bolts were evenly torqued no
    aluminum/oil on bolts. The first engine about half of bolts were loose, real mess, oil everywhere YUCK
    Took a day to clean even before disassembly.
    At this point just thinking about new rings for the second block.
    What's a good cleaner for the pistons?
    Any thoughts?

  13. #12
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    Re: 4.6 N* Cylinder walls

    Whatever you use, DO NOT use Scotch-Brite. Don't even let it near the motor.

  14. #13
    tero is offline Cadillac Owners Member
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    Re: 4.6 N* Cylinder walls

    ]

    ----------

    [/COLOR]that's a for sure!
    I pulled all the pistons out of the second block, cross hatch looks good, rings were definitely in bad shape.
    Planning to rering, replace rod bolts, likely new rod bearings, head stud kit and gaskets.
    I was able to pull the pistons without separating the block halves...just don't want to mess with the lower end, it was sealed up nicely, virtually no leaks.
    Will there be a problem just reusing the crankshaft bolts? And i'm hoping to reinstall pistons without splitting block.
    Sure it would be easier, but like i said don't want to go there.

  15. #14
    tero is offline Cadillac Owners Member
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    So Where do I Go From Here????

    I bought a '97 Eldorado from a salvage with minor body damage and a head gasket leak.
    No big deal right? Change gaskets, studs...whtever.
    I dropped the engine out the bottom, with the help of a FSM...easy.
    Turns out the engine has a cracked cylinder so i scrapped it.
    Picked up a '99 engine that was all carbonned up (old man motor never driven over 30mph)
    Engine was less intake, exhaust manifolds and front cover.
    Sure clean it up, change rings, rod bearing and bolts, and put together. Right?
    Ya sure.
    Now it turns out that the pistons and heads are different from one year to the next.
    '97 engine (block stamped '96) pistons have reliefs cut in them '99 does not
    heads are different, intake and exhaust ports are different
    manifolds just aren't going to work if i swap
    Can i buy new pistons with reliefs and use them in the '99 block?
    Do i just build the '99 block and find the right manifolds, and change a few sensors?
    At this point i'm scratching my head.
    Any thoughts would help

  16. #15
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