308 rear main seal alternative

devin
devin Member
in The Flathead Forum
Greetings, I'm receiving a 308 long block soon and will be swapping all the parts from my cracked motor. While I have access, I thought I would swap out the existing rear main seal with a Mopar?? one. Can anyone clarify which one for me and if this is a good idea. Thank you.

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  • devin
    devin Member
    I should clarify that this is for my '52 Twin H Hornet 308
  • Glowplug
    Glowplug Expert Adviser
    edited March 2020
    Put the Original style seal into your new block.  You are starting with a bare block and that seal will give best service. Dale cooper has these seals with the gasket sets he sells or separate if seal only required.
  • devin
    devin Member
    Glow Plug and Ken U-Tx than you for your generous wisdom! I will abandon the Mopar trick and follow your advice. I just ordered some goodies from Mr. Mass. I'll get back in touch with him.
    Once again thank you!!! Stay safe

  • Kdancy
    Kdancy Senior Contributor
    Prier discussion-

    Rob FayetteRob Fayette Posts: 101Expert Adviser
    I sent an email to Best Gasket asking why they recommend to not apply sealant to the ends of the rope seal.  This is the reply I got back.
    Rob 

    RE: 5206 Rear Main Rope Seal kit question

    Roy Lucero<roy@bestgasket.com>
    3/21/2019 11:44 AM
    To  ROB FAYETTE  
    Rob
    We do not recommend sealant on the ends or our GraphTite rope because the sealant will harden and actually damage the rope causing a potential leak passage.

     Other people might recommend sealant on the ends of the old style asbestos rope., not sure though.  

    Roy Lucero

    Best Gasket

    www.bestgasket.com

    Ph (888) 333-2378 - Ph (562) 699-6631 - Fax (562) 699-5034


  • Kdancy
    Kdancy Senior Contributor
    Added from another post-

    Ol racer Posts: 2,495Senior Contributor

    October 2017 edited October 2017

    Tip on Installing a Rope Rear Seal 'In Chassis'..My Hudson seal drip was annoying so figured simply roll in a Neoprene Seal, however, afterward dripped worse. Like I mentioned above, crank seal journal may have minute scratches, or the cap groove is slightly larger.
    After researching learned a Rope Seal is far more 'forgiving' however modern Rope Seals in gasket sets (except Best Seals) are made from inferior material & unreliable, thanks to E.P.A. Reg's.  Fortunately, I had an old Gasket Set with 'old material' Rope seal, but had to figure how to roll it up over the crank...Here is what I did...

    Simply take a 12Pt curved wrench (also called starter, hoop, or half-moon wrench, but needs to be a 12Pt) then patiently loosen the three 1'4" bolts right above the crank, but do not unscrew them too far and pry back the plate slightly. I didn’t have a 12Pt so I made a wrench. You need put a slight bend on handle to clear a rear Plate Bolt at 3:00 and 9:00. (Pic below)

     Next soak the Rope Seal overnight in light Oil. (Yes, need to soak old material) then form fit the Seal in the Main Cap using a large socket or Pipe. I formed it to be .029 to start in groove then remainder was .031 - .034 depth. Next, buy a cheap Sneaky Pete Tool (Lisle #27000), use the Corkscrew provided to pull the old seal out while rotating crank, then discard the 3 tiny Lisle 'grab' attachments designed to pull the new Seal up (which won’t work), and instead, insert the Lisle piano wire above the crank then hook the end of the wire into the Rope Seal as far as possible & approx. 1/4" back from Seal end. Next, start the Rope Seal into the upper groove then rotate the crank while pulling on the piano wire handle. (suggest practice with pulling the old seal around). Lastly, trim the top Seal Ends flush then place a dab of Black Permatex RTV on each end and re tighten three top bolts..

    For the Cap, Fit the Seal in groove tightly and leave .015 protrude out of Cap providing a 'crush' when Cap is torqued 75 - 80lbs.

     I’ve done it twice now while lying on my back with no drip.... The key thing is don’t back the 1/4" screws all way out and be patient fitting the wrench on the bolts. Once get the rythm its pretty easy...This install was in Stepdown Hudson with Hydromatic.

    As a Foot Note: The Best Gasket Co Graphtite Rope Seal measured .030 before fitted in Main Cap groove so probably would pull up easier over the crank. It requires pining in the Cap so elected installing N.O.S Rope.

     

    Ol racer Posts: 2,495Senior Contributor
    Attached picture showing hooking Seal to slide up over the Crank after seal compressed using Main Cap.  Note The Sneaky Pete Tool is actually reversed from theit instruction since the 'Fingers' provided slip right off.


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