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Rear main seal leaks on B.B. #2741977
02/11/20 03:14 PM
02/11/20 03:14 PM
Joined: Jan 2003
Posts: 6,363
Abilene, Texas
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fastmark Offline OP
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Abilene, Texas
I’ve got two customers who have brought their motors in for rebuild and both complains of leaks in the rear main and are asking about the best billet rear main seal kit out there. One was asking about using an old rope seal. I’ve never really had problems but am asking what everyone is using that has had problems and fixed their leaks.

Re: Rear main seal leaks on B.B. [Re: fastmark] #2741984
02/11/20 03:29 PM
02/11/20 03:29 PM
Joined: Mar 2003
Posts: 1,417
Martinsville, IN
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cdwmotorsports Offline
pro stock
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Martinsville, IN
I have a block missing one so I’ve been looking at billet ones. 440source has one it’s about $50 for the kit with the bolts. I have not used it and will monitor this.


eBay-cdwmotorsports
Re: Rear main seal leaks on B.B. [Re: fastmark] #2741986
02/11/20 03:31 PM
02/11/20 03:31 PM
Joined: Mar 2007
Posts: 3,275
West Coast, USA
jbc426 Offline
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West Coast, USA
There seems to be a trick to getting them not to leak. There are some great threads in the archives on here about numerous people's struggles to get them leak free.

Hughes sells a billet seal holder too. Superformance sells a nice rear seal kit. Also, keep in mind that the two oil pan bolts that thread into the seal holder are shorter than the rest of the pan bolts. Make sure you pre-fit the ones you are going to use to make sure they don't bottom out in the seal holder.

Last edited by jbc426; 02/11/20 03:32 PM.

1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
Re: Rear main seal leaks on B.B. [Re: jbc426] #2741989
02/11/20 03:34 PM
02/11/20 03:34 PM
Joined: Jan 2003
Posts: 13,319
Marion, South Carolina [><]
an8sec70cuda Offline
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Posts: 13,319
Marion, South Carolina [><]
I've never had any issues using a stock retainer and just offsetting the seal in the cap so the ends of the seal doesn't line up w/ the edge of the retainer.
I always use Fel-Pro seals.


CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
Re: Rear main seal leaks on B.B. [Re: an8sec70cuda] #2741992
02/11/20 03:44 PM
02/11/20 03:44 PM
Joined: Jan 2003
Posts: 6,988
Warren, MI
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Jerry Offline
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ours are made from billet aluminum and use a dual oring seal on the sides of the RMS. there are generally two locations where these leak, 1 is the seal itself. ideally if using a modern split seal, you want to offset the cut away from the joint where the rear main seal touches the block. I slide mine in about 30 degrees offset to the mating surface and apply some rtv to the seal tips to help close the gap. the other place these tend to leak is the crappy trapezoidal shaped rubber seals that always seem to squeeze out. we replaced this with o ring seals on the side. I do recommed adding some rtv to the mating surface of block and the RMS just to make sure there is no weeping there as well.

our billet RMS is $49.00 plus shipping with new bolts and the oring seals.


Superior Design Concepts
2574 Elliott Dr
Troy MI 48083
jerry@sdconcepts.com
www.sdconcepts.com
Facebook page: Superior Design Concepts
www.bcrproducts.com
Re: Rear main seal leaks on B.B. [Re: Jerry] #2742070
02/11/20 08:20 PM
02/11/20 08:20 PM
Joined: Aug 2003
Posts: 43,007
Bend,OR USA
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Cab_Burge Offline
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Bend,OR USA
I've used stock rear main seal holders for a lot of years on stock blocks and 1 or 2 on after market blocks with no sealing issues. I have several in stock now from broken blocks.
I buy the seals in bulk and the last batch, not sure of the manufacturer, had issues on the depth of the sealing surfaces on a race block, I ended up using some of the older main seals I had and they worked good up What showed me the problem was there was no marks from the seal edge on the grease I put on the seal surface as a lube, IE no contact with the crankshaft shock
I now installed the seal holder with no side seals and check the seal contact to the crankshaft before adding the side seals up scope
I don't stagger the seals either but I try to remember to use a small dab of adhesive silicone between the seal ends up


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Rear main seal leaks on B.B. [Re: an8sec70cuda] #2742173
02/12/20 08:37 AM
02/12/20 08:37 AM
Joined: Nov 2004
Posts: 7,274
s.w.fl
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bonefish Offline
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s.w.fl
Originally Posted by an8sec70cuda
I've never had any issues using a stock retainer and just offsetting the seal in the cap so the ends of the seal doesn't line up w/ the edge of the retainer.
I always use Fel-Pro seals.
This is all ive ever done,even on after market blocks and have had goods results.im no pro by a long shot.

Re: Rear main seal leaks on B.B. [Re: Cab_Burge] #2742198
02/12/20 10:55 AM
02/12/20 10:55 AM
Joined: Jan 2003
Posts: 6,363
Abilene, Texas
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fastmark Offline OP
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Abilene, Texas
Originally Posted by Cab_Burge
I've used stock rear main seal holders for a lot of years on stock blocks and 1 or 2 on after market blocks with no sealing issues. I have several in stock now from broken blocks.
I buy the seals in bulk and the last batch, not sure of the manufacturer, had issues on the depth of the sealing surfaces on a race block, I ended up using some of the older main seals I had and they worked good up What showed me the problem was there was no marks from the seal edge on the grease I put on the seal surface as a lube, IE no contact with the crankshaft shock
I now installed the seal holder with no side seals and check the seal contact to the crankshaft before adding the side seals up scope
I don't stagger the seals either but I try to remember to use a small dab of adhesive silicone between the seal ends up


That’s my experience. I had one SB that I never could fix but that was long ago.

Re: Rear main seal leaks on B.B. [Re: fastmark] #2742201
02/12/20 11:07 AM
02/12/20 11:07 AM
Joined: Aug 2003
Posts: 8,779
Mt.Gilead, Ohio
OhioMopar Offline
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Mt.Gilead, Ohio
I used the Mancini RMS kit. No leaks.


1969 Dart GTS 340
1969 Super Bee X9 N-96
1969 Coronet R/T X9 N-96
2015 Dodge Dart GT
2019 Ram 2500 Big Horn.
Looking for the original block for my Bee. The last 4 are 7449






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