Early Slant 6 Rebuild

Slant 6 Engines

  1. chinze57

    chinze57 Push Button tranny and a Slant 6 that'll never die FABO Gold Member

    Messages:
    261
    Likes Received:
    34
    Joined:
    Nov 6, 2019
    Location:
    Georgia, USA
    Local Time:
    7:34 AM
    Hey y’all, it’s getting to be about time to rebuild my slant 6.

    I’ve recently developed a leak at the rear main seal, and my mechanic doesn’t think it’s worth having replaced until the engine is rebuilt. A little history on the engine, I know the previous owner who knows the owner before him. Neither of them ever had it rebuilt, and the guy who had it before me (an idiot) probably only ever did one oil change in the 5+ years he had the car. It was in bad shape when I got it, so I’ve known this was coming.

    Is this something I could fairly easily do myself or is it something that would be best done by someone with experience?

    I live in Georgia, near Atlanta, so if anyone knows someone who does quality work on a /6 around here please let me know.
     
  2. my68barracuda

    my68barracuda Well-Known Member

    Messages:
    1,451
    Likes Received:
    1130
    Joined:
    Dec 6, 2009
    Location:
    Indianapolis IN
    Local Time:
    7:34 AM
    To get to the rear main seal on a slant you will need to drop the oil pan.
    To get the oil pan out if you are working on an A body you will need to at least remove the motor mounts and tilt and lift the engine up.
    After doing all of that, trying to get the top half of the seal changed, trying to get the oil pan re sealed, while working on an engine in chassis,,, is a lot of effort without a great chance of success.
    I would pull the engine to change the rear seal, or wait and change it when the engine is rebuilt.

    It would be worth the time to do a quick investigation as to why it is leaking oil,,,
    Did some of the oil pan bolts get loose?
    Is there excess / non vented pressure in the crankcase from a plugged PCV system or road draft tube?
    Has piston ring blow by got so bad that the crankcase vent system can’t keep up?
    Is there thrust bearing worn and the crank end play is out of specification?
     
  3. Johnny Grand

    Johnny Grand Member

    Messages:
    9
    Likes Received:
    3
    Joined:
    Nov 21, 2019
    Location:
    indiana
    Local Time:
    7:34 AM
     
  4. Johnny Grand

    Johnny Grand Member

    Messages:
    9
    Likes Received:
    3
    Joined:
    Nov 21, 2019
    Location:
    indiana
    Local Time:
    7:34 AM
    Buy the book " how to rebuild and modify slant six" by Doug Dutra. Well worth it even if you don't rebuild it yourself. I was always told, "if you want something done right, do it yourself". Lots of good help on this site. Have at it.
     
    • Like Like x 1
    • chinze57

      chinze57 Push Button tranny and a Slant 6 that'll never die FABO Gold Member

      Messages:
      261
      Likes Received:
      34
      Joined:
      Nov 6, 2019
      Location:
      Georgia, USA
      Local Time:
      7:34 AM
      The oil pan is sealed tight. The leak is coming right at the bottom of where the engine and transmission meet.

      As to why it’s started leaking in the past 2 weeks, no clue. I’ve been driving with this motor for about a year now. I had a ton of maintenance done when i first bought the car, which included new timing, new oil pump, new valve cover gasket and oil pan gasket, etc. And have had one tune up done and done another myself. But it’s not a very fun leak, I lost a quart of oil in ~2 weeks. Previously i went almost 2 months before i was noticeably down (not even a quart, maybe half a quart), And by then i was due for An oil change. But now it’s leaking like a sieve.
       
    • my68barracuda

      my68barracuda Well-Known Member

      Messages:
      1,451
      Likes Received:
      1130
      Joined:
      Dec 6, 2009
      Location:
      Indianapolis IN
      Local Time:
      7:34 AM
      Then, I would pull up the timing for the engine rebuild and fix the rear main seal when the engine is redone.
      That will save you the couple of hundred dollars that you will pay someone to just change out the rear seal and you stand a much better chance of the work being done correctly with the rear seal being changed with the engine out of chassis.
       
      • Thanks! Thanks! x 1
      • teringer

        teringer ase master hall of fame FABO Gold Member

        Messages:
        851
        Likes Received:
        204
        Joined:
        Feb 22, 2011
        Location:
        kenly nc
        Local Time:
        6:34 AM
        make sure the pcv valve isn't stopped up
         
        • Agree Agree x 1
        • dddDuster

          dddDuster Well-Known Member

          Messages:
          191
          Likes Received:
          154
          Joined:
          Sep 21, 2014
          Location:
          Eaton, CO
          Local Time:
          5:34 AM
          Are you certain it’s motor oil? Sudden huge leaks don’t happen that often to the main seals. Transmission seals, especially in manuals will let go on a guy...
           
        • RustyRatRod

          RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

          Messages:
          65,845
          Likes Received:
          39150
          Joined:
          Jun 7, 2010
          Location:
          Georgia
          Local Time:
          7:34 AM
          I'm doing the bottom end on mine right now.

          VIXEN MOTOR REPAIR.jpg
           
        • chinze57

          chinze57 Push Button tranny and a Slant 6 that'll never die FABO Gold Member

          Messages:
          261
          Likes Received:
          34
          Joined:
          Nov 6, 2019
          Location:
          Georgia, USA
          Local Time:
          7:34 AM
          It’s definitely motor oil. Haven’t had to put in any trans fluid in a year, it’s still got plenty. But ran low on motor oil 2 weeks after an oil change. Oil pan is tight and back oil drain plug is tight
           
        • my68barracuda

          my68barracuda Well-Known Member

          Messages:
          1,451
          Likes Received:
          1130
          Joined:
          Dec 6, 2009
          Location:
          Indianapolis IN
          Local Time:
          7:34 AM
          Rusty, are you changing out the rear seal? I believe you are changing the bearing but not pulling the pistons and rods,,,
           
        • RustyRatRod

          RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

          Messages:
          65,845
          Likes Received:
          39150
          Joined:
          Jun 7, 2010
          Location:
          Georgia
          Local Time:
          7:34 AM
          Yes. It had the old rope seal. Dang right I am changing it. lol And I did leave the pistons in place since I'm not pulling the head. I just yanked the crank out, cleaned it all up and put new bearings in it.
           
        • my68barracuda

          my68barracuda Well-Known Member

          Messages:
          1,451
          Likes Received:
          1130
          Joined:
          Dec 6, 2009
          Location:
          Indianapolis IN
          Local Time:
          7:34 AM
          It will be good for another 50 years!
           
        • RustyRatRod

          RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

          Messages:
          65,845
          Likes Received:
          39150
          Joined:
          Jun 7, 2010
          Location:
          Georgia
          Local Time:
          7:34 AM
          Probably. That's actually what I'm counting on. Last compression test, it had 155-160 on all six so the top end is great. It doesn't smoke a lick. So the ring seal is good. With the new bearings, oil pump and timing set it should be golden. Remember when I keep saying I "might" leave it a slant? Yeah. That.
           
        • my68barracuda

          my68barracuda Well-Known Member

          Messages:
          1,451
          Likes Received:
          1130
          Joined:
          Dec 6, 2009
          Location:
          Indianapolis IN
          Local Time:
          7:34 AM
          Don’t want to get the original post off track, but you may want to do valve seals if they are OE.
           
        • RustyRatRod

          RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

          Messages:
          65,845
          Likes Received:
          39150
          Joined:
          Jun 7, 2010
          Location:
          Georgia
          Local Time:
          7:34 AM
          I looked at them when I did the valve adjustment. They are soft and look pretty new.
           
        • BillGrissom

          BillGrissom Well-Known Member

          Messages:
          7,394
          Likes Received:
          411
          Joined:
          May 10, 2009
          Location:
          Sacramento
          Local Time:
          4:34 AM
          If the compression measures fine, the engine doesn't need a rebuild and you would risk f'ing up your engine. All oil seals and gaskets can be replaced from outside with the engine in the car, except for the head gasket (usually an overheating issue from coolant loss). It is a pain removing the oil pan, but after that the rear seal isn't hard to change. It isn't like new cars which require removing the transmission and flexplate (since they slide over the crankshaft to seal better). It is the same PN as used in the Hemi engine. I haven't seen the rope seal that Rusty mentions. Perhaps that was original, but my 1964 had the 2-part rubber seal.

          While in there, insure that the tapped holes in the aluminum seal holder for the oil pan bolts weren't stripped by some gomer (common). Now is the time to fix that with a Heli-coil insert. Indeed, that could cause the oil pan gasket to leak right where the rear crank seal would leak. Insure those bolts are tight and don't torque beyond the spec!. If they are stripped, you might be able to screw a stud in the holes to reach unmolested threads, then a nut, or use a slightly larger metric bolt for now until some day you have the oil pan off to fix it right. I used a better silicone oil pan gasket (Real Gaskets of TN) since getting that pan off is a hassle.
           
          • Thanks! Thanks! x 1
          • RustyRatRod

            RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

            Messages:
            65,845
            Likes Received:
            39150
            Joined:
            Jun 7, 2010
            Location:
            Georgia
            Local Time:
            7:34 AM
            The rear main seal cannot be replaced from the outside and if his has the old rope seal like a lot of them did, that's a major source of contention with an oil leak.
             
          1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
            By continuing to use this site, you are consenting to our use of cookies.