Gasket surface prep?

Discussion in '2005+ Mustang GT 4.6L Tech' started by eighty6gt, Jun 19, 2017.

  1. eighty6gt

    eighty6gt forum member

    Posts:
    2,424
    Likes Received:
    3
    Joined:
    May 9, 2011
    I looked around, not much about this on here. Nothing!

    I'm cleaning up my cylinder heads, lots of crap/corrosion at the edges near the valley and on the exhaust side. My cylinder head guy cleaned up the exhaust port area a little bit with ... something or other. Seemed like more corrosion the further back you got on where the header mounts.

    Mostly I need to know about the head gasket sealing area, is anyone using surface conditioning pads? This is against practice but maybe there is a silver bullet solution. I've gone over it about 3x with gasket remover, seems fairly smooth but there are a lot of rough areas outside of where the original gasket sat.
     
  2. drive_55_not

    drive_55_not forum member

    Posts:
    531
    Likes Received:
    0
    Joined:
    Sep 29, 2011
    Location:
    NC
    Seafoam and 2000 grit sandpaper will remove the old gasket layer net you a mirror finish.

    .
     
  3. o2sys

    o2sys forum member

    Posts:
    4,124
    Likes Received:
    0
    Joined:
    Jun 26, 2011
    Location:
    NY/NJ
    When I took my heads of it wasnt that bad. Just lots of carbon build up. Used gasket remover and a plastic scraper till everything was spotless.
     
  4. Brick

    Brick forum member

    Posts:
    96
    Likes Received:
    0
    Joined:
    Jan 23, 2011
    Location:
    East Central Ohio
    This is in the 4.0 section, but I'm speaking with my experience on the 4.6 3V...

    I think it was on this board where I read about this topic when I had to have one of my heads resurfaced. The advice was not to use any scotchbrite, steel wool, or any kind of do-it-yourself method of prepping a head surface for these newer motors. The level of smoothness required to seal the MLS head gaskets that the 4.6 uses can only be achieved from a machine shop with the proper kind of CNC mill. Seems to me like I remember it needed to be a RA (Roughness Average) of 10 or less.

    Hopefully someone with more experience building these motors can confirm this... BruceH?
     
  5. skwerl

    skwerl tree hugger

    Posts:
    14,922
    Likes Received:
    11
    Joined:
    Aug 6, 2011
    Location:
    central Florida
    If it is outside the gasket area then I wouldn't be concerned about it, as long as it is flat and not going to interfere with the gasket sealing. Getting too worked up about it may end up with you screwing up the gasket sealing area.
     
  6. RocketcarX

    RocketcarX 95% of my weight is fuel

    Posts:
    1,602
    Likes Received:
    7
    Joined:
    Jul 19, 2011
    Location:
    Burton Texas
    Have them hot tanked at the machine shop or pressure wash them. You can't hurt the heads washing them. Make sure to blow them out thoroughly with compressed air before installation.
     
  7. BruceH

    BruceH BBB Big Bore Boss 322 Staff Member

    Posts:
    13,802
    Likes Received:
    3
    Joined:
    Sep 13, 2009
    Location:
    Pacific Northwest
    Solvent clean and scrape with plastic scraper. It takes time but works. Anything else will change the ra.

    BTW have you checked the head for straightness?
     
  8. eighty6gt

    eighty6gt forum member

    Posts:
    2,424
    Likes Received:
    3
    Joined:
    May 9, 2011
    Straightness, that's a great question... I have been trying - I am probably going to have to get a machinist rule from summit or jegs since I can't find one here. Have you ever had a head that had a bend or twist? I just cleaned out my coolant reservoir and it seemed to have oil in it. I wasn't sure until I actually got it full of soap and was cleaning out the bottom. You'd think oil would remain on the surface, but...

    I have cleaned and pressure washed the crap out of these heads, they were unbelievably filthy. I have not used any abrasives on the sealing surface, only gasket remover and plastic scraper blades.
     
  9. 01yellerCobra

    01yellerCobra forum member

    Posts:
    1,599
    Likes Received:
    5
    Joined:
    Apr 11, 2011
    Location:
    San Diego, CA
    That would also be called warping. And it's been known to happen. I managed to warp two 4V heads when my engine overheated.
     
  10. BruceH

    BruceH BBB Big Bore Boss 322 Staff Member

    Posts:
    13,802
    Likes Received:
    3
    Joined:
    Sep 13, 2009
    Location:
    Pacific Northwest
    IIRC the modular heads need no more than .001" per 4".

    If the motor was assembled with tty hardware it's probably ok. I'd still get the machinists straight edge and check. The mls head gaskets are sensitive to having the correct ra and straightness.

    This brings up another topic. If the heads or block need to be machined make sure the machine shop can finish with the correct roughness average for a mls head gasket motor. Believe it or not there are still machine shops out there who will machine your motor like it was a sbc from a 1976 Monte Carlo. The usual selling point is something like "we put together race motors so your little modular motor won't be a problem" Times and machining requirements have changed greatly since machining the sbc or bbc was figured out.

    But I digress. Good luck with the build.
     
  11. eighty6gt

    eighty6gt forum member

    Posts:
    2,424
    Likes Received:
    3
    Joined:
    May 9, 2011
    A thou in 4 is actually pretty curvy. I'm going to get my machinist to make me a piece of steel on the mill that is a lot better than that, compare.
     
  12. BruceH

    BruceH BBB Big Bore Boss 322 Staff Member

    Posts:
    13,802
    Likes Received:
    3
    Joined:
    Sep 13, 2009
    Location:
    Pacific Northwest

    ??? That's the Ford spec as I remember it. No more than .001" deviation over a 4" length.

    The straight edge shouldn't have any measurable difference throughout it's length, the .001" per 4" is the head surface.
     

Share This Page