Rear main seal install screw up. Need help!

Engine, Transmission & Driveline

  1. jake

    jake Senior Member

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    Leaking again, took it apart today and now looking at it, I think I installed it backwards. Take a look at the pics and let me know please. Going to remove and clean everything and install new one but want to make sure the new one is in the right direction. Thank yous in advance!
    _3QeTfZBlSdSaunoeeJ4sduHPvfmu6EkbbFBS8aq27ZrDvbeLgMejvfHZJW4L7vbKChAK40q8iKimcEbCLG=w651-h867-no.jpg
    nwKziZLiQ469kqdPeP1TR0myv2iygNCBaqX1idsGbSx9wW91J85gz_19C_RKegc7Q33yT7mMutRe7W48Vx=w1157-h867-no.jpg
    NnxvTqBKTLqKrysP0huh7RgJQFj19ChHxg7ybvsZOAM5nc9O-Wx000cXo89B7DqD07ZRP9MNE_STxX-lJX=w1157-h867-no.jpg
     
  2. CBODY67

    CBODY67 Senior Member

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    Years ago, there was a letter to the "fixer column" n Popular Science magazine, or possibly Popular Mechanics, where the guy had replaced a seeping rear main seal, only to have the new one leak at least as bad. What went wrong, he wondered?

    The reply mentioned a knurl pattern on the middle area of the seal face. They are designed to "pump" any oil that gets past the inner lip seal back toward the crankshaft. If put in backward, it "pumps" it to the outside. First time I'd ever heard of that! Not sure if that might be operable in your case or not, but wanted to mention it.

    Otherwise, some seals re-locate the main lip seal contact area to not be where the prior seal touched the spinning shaft. "New territory" to seal against, even if it's .020" different. So looking for a slight groove in the rear main seal surface on the crank might be operative? Perhaps some replacement seals are a slight bit undersized (thicker seal) in that area, for that reason?

    Hope you get it all figured out!

    CBODY67
     
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  3. commando1

    commando1 Mr. Normal FCBO Gold Member

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  4. jake

    jake Senior Member

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  5. commando1

    commando1 Mr. Normal FCBO Gold Member

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    Like said before...
    1. Stagger the gaps tween the seal and the cap.
    2. Don’t be stingy with the RTV.
     
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  6. rkrochen

    rkrochen Active Member

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    Yes from what I can see it looks correct.
     
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  7. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    I'm just going to toss this out there... Are you 100% sure it's the seal?

    I've seen where a leaky oil sender drips enough oil around the bellhousing to mimic a bad rear seal.
     
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  8. jake

    jake Senior Member

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    Yes, first thing I checked.
     
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  9. jake

    jake Senior Member

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    Well, I put a new one in, going let it set up tonight and tomorrow and then give her a trail run. I cut a coil out of the spring on the oil pump to see if it lowers the pressure a little. On a cold start up, she runs at 85 psi. I will let everyone know.
    I have it down to about 4.5 hours with a quick lunch, sad, very sad.
     
  10. 73Coupe

    73Coupe Well-Known Member

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    Take a photo of the crank where the seal goes and post here.
    Is there a groove or any corrosion on the surface?
     
  11. commando1

    commando1 Mr. Normal FCBO Gold Member

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    Too late.
     
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  12. 73Coupe

    73Coupe Well-Known Member

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    That's because the oil is cold at startup and hard to push through the engine. I wouldn't alter the pressure relief spring at all. Put in a new spring.
     
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  13. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    Cutting a coil out will make it shorter, but it also makes it stiffer.
     
  14. jake

    jake Senior Member

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    I did not get a photo but it was clean and looked good.
     
  15. CBODY67

    CBODY67 Senior Member

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    What oil pump is making that much cold pressure with WHICH oil? What's the "been run for 30 minutes" hot base idle pressure?
     
  16. jake

    jake Senior Member

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    10w-30, 25psi at temp at idle
     
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  17. commando1

    commando1 Mr. Normal FCBO Gold Member

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    I'd go 10W-50 or 5W-40 in that case although I would prefer returning to a stock pump spring first.
     
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  18. imperialman

    imperialman Active Member

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    I have been following this with interest and hope it works out for Jake.

    Something good that has come from his issues is that its reaffirmed my procrastination with replacing the leaking rear main seal on my 78 NYB
    :lol:
     
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  19. CBODY67

    CBODY67 Senior Member

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    To me, the "at temp" pressure looks good, as does the oil viscosity used. I'll concur that a stock oil pump spring might be a good option.

    Used to be that 10psi/1000rpm was the best criteria for doing an oiling system. With better oils and related basestocks (even for non-synthetics), this rule has tended to soften a bit. In addition to the real need for heavier oils for perceived better protection.

    For years, I ran Castrol GTX 20W-50 in my '70 Monaco 383 "N", with good results. With other oils, it would start to bang-out just before the shift points. Going to that oil stopped that. At the time, many called it "motorcycle oil". I figured if it was good enough for Autobahn burners, with their smaller engines running at higher rpms, with their generally narrower bearing widths, it ought to be great in a big American V-8 (with wider bearings) at our normal highway speeds. Used it in my '77 Camaro 305 from its first oil change. But when the 305 was swapped for a 355, it started that engine's life on Valvoline 30, then went to 20W-50. I could tell a difference in response and power, just a very small amount, but enough it didn't feel right. So I changed to 10W-40 and everything came back. Heavier oils take more power to drive the oil pump, affecting power and economy . . . enough that OEMs seldom use anything heavier than 5W-30 now in cars w/gasoline engines. I did end up with Rotella T6 5W-40 syn later on, for the zddp levels (which are still above the old "SL" level, usually greater than 1200ppm).

    When we built the 355, I spec'd a high volume pump, but with a standard spring. Just wanted something better than stock. End result is that with modern oils, much of what we knew "as good" in the '60s needs some updating in modern times.

    Just some thoughts,
    CBODY67
     
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  20. savoy64

    savoy64 New Member

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    i thought the knurl was made for the old rope seal---new cranks-no knurl-rubber seal....