this horse has been beat to death , but------

Big Block A body Tech

  1. famous bob

    famous bob mopar misfit FABO Gold Member

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    I have had a rear mainseal leak since day one , I have finally found out why, after 3-4 times trying to fix it .
    The main seal cap is not made right, or the bolt holes in the block are offset from perfect, or the crank is setting in the block crooked . Don't think it the crank cause all pistons were exactly the same deck heigth when built , if crank was crooked one side would be off , compared to the other side. I installed the main cap after cleaning it up w/o the side seals , letting it center itself on the crank , ( no bolts) , one side of the cap is way closer to the block than the other side . I redrilled the bolt holes out bigger and checked the bolts , they (allen heads) were .005 bigger than stock , slightly adding to the problem.
    I still haven't figured out how to seal the cap on the sides , w/ the engine in the car ,
    getting the whole mess clean of all oil would be a bitch , not to mention how to get sillicone up in there to seal it from the outside.
    I have found a billet main cap that is offered by an old funny car racer, and not like the current ones on the market, ordered it this morning. If its the same way , sealing the sides will be a bithch , 73 yrs old and laying on a piece of cardboard in the floor aint fun any more !

    Sorry for the long rant m "more to come !"
     
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    • Donnie514

      Donnie514 FABO Gold Member FABO Gold Member

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      OK, this is a big block...right?
       
    • krazykuda

      krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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      If you replace the main cap, it has to be remachined to match your engine - align bored... You will have to pull the engine out and strip it down to the block to get it machined... When they machine a block, they rough bore the caps and mains, then bolt them together and align bore the crank bores so they are all lined up properly - that's why you can't mix and match the caps and have to keep them in the proper order that they were machined on the block....
       
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      • krazykuda

        krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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        Oh yeah, big blocks have that funny rear seal, not like the small block....

        You may not have to get it machined if it's a big block... I'm more familiar with small blocks...
         
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        • toolmanmike

          toolmanmike FABO Staff Staff Member FABO Gold Member

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          Somebody makes a rear seal retainer to address this.
           
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          • MOPAR4Me

            MOPAR4Me FABO Gold Member FABO Gold Member

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            Not sure but think this may be what you are referencing:

            Mancini Racing Billet Rear Main Seal Retainer

            "Fits: Big Block, Mopar

            Billet aluminum rear main retainer. It uses double o-ring on each end to seal the cap to the block. This retainer is designed to hold the proper diameter to clamp the rear main seal properly.

            Sold in kit form with Cap, 4-O-ring seals, Rear main seal, 2 - alignment pins for easy installation and socket head bolts"

            mancini-racing-billet-rear-main-seal-retainer-31.gif
             
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            • MOPAR4Me

              MOPAR4Me FABO Gold Member FABO Gold Member

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              Last edited: Dec 31, 2019
            • MOPAR4Me

              MOPAR4Me FABO Gold Member FABO Gold Member

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            • mycuda

              mycuda FABO Gold Member FABO Gold Member

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              Have to agree. Although didnt verify your
              Observations.
              I built this B block back in 1992.
              383 .60 over nothing fancy 11:1 open chamber ported heads.Gear drive.
              This thing leaked from day one. Interesting.
              Mainly after 30 minute drive or so.
              Nitrous playtime sure didnt help.
              But engine strong.

              I didnt want to think something I did or didnt do....
               
            • Darter6

              Darter6 Well-Known Member

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              Confucius say, It ain't a MOPAR if it don't leak !:lol:
               
            • fklskv

              fklskv Well-Known Member

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              • famous bob

                famous bob mopar misfit FABO Gold Member

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                The engine came out of as 66 Chrysler still mated to the trans, it had a rear main leak when I tore it down, which I didnt pay much attention to because I was not going to use anything but the block. Anyway, I have found that the cast rear maim seal cap is .061 shifted to the pass side , . Waiting on new one --------
                 
              • mycuda

                mycuda FABO Gold Member FABO Gold Member

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                Interesting.
                My 383 was out of 67 New Yorker....
                 
              • famous bob

                famous bob mopar misfit FABO Gold Member

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                My deck height only had to have .003 taken off to be perfect , I think the machine work on the early blocks might have been real close . ??????????
                Cast main seal cap , not so much.
                 
              • toolmanmike

                toolmanmike FABO Staff Staff Member FABO Gold Member

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                I always heard the Chrysler engines were carefully assembled. More like they were factory blueprinted.
                 
              • famous bob

                famous bob mopar misfit FABO Gold Member

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                I know they have been way closer to perfect than any of the chevy blocks I`ve messed with, they have been off a mile from what the factory said.
                The two 426 hemi`s I had were spot on perfect !!
                 
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                • RPMagoo

                  RPMagoo Just An Old Motorhead

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                  -- Same here, at 75. -- Amen Brother.
                   
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                  • RAMM

                    RAMM Well-Known Member

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                    Yeah that would be me, I haven't had another big Mopar leak since. J.Rob
                     
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                    • MOPAR4Me

                      MOPAR4Me FABO Gold Member FABO Gold Member

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                      May have missed it, but aside from the cast rear main seal cap shift issue, is your install past/planned also including the seal position rotation offsetting in relation to the seal retainer/block flange mounting area?

                      159691-bfb45d4a15918da7faa7f55425bf5326.jpg
                       
                      Last edited: Jan 1, 2020
                    • w2dart

                      w2dart Member

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                      I built one years ago. 3-4 rear main seals later, found out it was a marine engine reverse rotation. Pulling oil out of engine.
                       
                    • famous bob

                      famous bob mopar misfit FABO Gold Member

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                      Well I haven`t got the pan back on yet , but the new seal cap came in yesterday , and is the neatest I`ve ever seen. CNC`d and fit like a glove, couldn`t have been any more perfect, centered the maim seal , fit the side of the block perfect and tite both sides.
                      I was kinda worried about the side rails tho , as tite as it fit the block . I got the bright idea of glueing the soft rubber side rails to the cap , using DAP fusion weld, a fast setting , glue anything ''but pure silicone'' , glue.
                      Held it on a flat surface for about 15-20 seconds in position while setting up, oiled the sides of the rails when installing, had to apply a little push in pressure on one side to get started, went in w/ a good amount of pressure to install, when it hit the circular part around the crank , I had offset about 3/8" , I could tell it pushed them together to mate, really happy w/ it ---------reworked the funny car windage tray to fit the reworked funny car pan , will install it today. Mwuay old ass wore out -----------more to come.
                       
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                      • oldkimmer

                        oldkimmer FABO Gold Member FABO Gold Member

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                        Glad to hear everything is working out. Kim
                         
                      • famous bob

                        famous bob mopar misfit FABO Gold Member

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                        PUT THE PAN AND WINDAGE TRAY ON TODAY, GOT THE RACK AND PINION BACK IN , JUST NEED TO GET A GOOD FILTER AND ADD OIL NOW. CAN EVEN RUN A REGULAR FILTER NOW AFTER REWORKING THE FAN SHROUD , HAVE HAD TO RUN A SHORT FILTER UP TO NOW.
                        I DID CHUCK THE FRONT MAIN STUDS UP IN MY LITTLE LATHE AND SHORTEN THEM, I CAN GET THE PAN OFF NOW W/O TAKING THE RACK AND PINION /STEERRING STUFF LOOSE .
                         
                      • famous bob

                        famous bob mopar misfit FABO Gold Member

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                        update/ got around to driving it yesterday, no leaks ! I highly recommend junking the stock main seal cap and buying a cnc`d billet one . About anybodies will probly work.
                        First time I haven`t had a leak on this 52 yr old barracuda !!---------fingurs crossed !
                         
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                        • fratzog lover

                          fratzog lover Well-Known Member

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                          The 383 had 2 different rear main seal journals. The knurled journal likes the original style seal.
                           
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