Mopar Performance had a #5 main with a relief cut to help keep oil pressure off the seal. The cut was on bearing surface the going from oil groove toward front of engine.
Rear Main leak above 3000 rpm only?
- Thread starter 72golddustermike
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vance.dykes
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thank you. also if the builder did not hone the cylinders correct that might add to this type of oil consumption. what say all ?
vance.dykes
Well-Known Member
for the c.i.d of that engine it should have fully grooved main barrings installed . oil is the cooler for all the force on that stroker.
He didn't say b or rb but here's the #5 bearing for a b engine. Don't see one for rb, I've got one someplace? You could do it yourself if bearing is full groove. Just file a Small groove on the forward face of lower bearing half to oil groove 180 degrees from oil supply hole. The idea is to relief oil pressure from seal side of bearing. Sure it isn't a gallery plug leaking? Had it happen to me. https://www.manciniracing.com/moanremabe10.html These are -.010 bearings.
vance.dykes
Well-Known Member
68Moparmaniac
Well-Known Member
Here's the knurling I'm talking about Mr 69Bee. This surface is only for rope style seals... you can disagree all you want but it is what it is. Neoprene seals require smooth surface. You put a rubber seal on this surface and you'll be doing it again before you know it. I know this from experience.
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vance.dykes
Well-Known Member
this is absolutely right full and split lip seals need a smooth surface just look at your trans seals.
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The fluoroelastomer split seal, (Viton) can work just fine on the crank with the directional grooves if you follow the installation instructions to the letter.
(Post # 10 in this "sticky" )
https://www.forbbodiesonly.com/mopa...-thread-on-rear-main-seal-replacement.127618/
Yeah, I'm old school and believe in "if it ain't broke, why fix it?" The only thing about the rope seal is that it can dry out if the engine sits for long periods of time. (New ones are not made of the same material as the original ones either. Thank you EPA) Some actually leaked from the factory. The Viton seal won't, or doesn't suppose to, dry out, and was the main reason that it was created.
Either seal, if not correctly installed, can leak. Over pressure of the crankcase will push oil past either one. If the split seal is installed backwards, it's guaranteed to leak. I'm not crazy about silicone sealer and would use Permatex #2 instead. The placement of the cap is of the utmost importance. As shown in the instructions of the Viton seal, careful measurements that are transferred from the block to the retainer and the centering, will insure proper retainer placement when installed. I've had good luck so far with the Viton seal and the side seals.
The leak that I do have is from not applying any sealer in the recessed cap bolt holes. Some pan gaskets don't completely cover this area and oil can make it's way past the gasket. It only leaks after I jack the front of the car up for a period of time then let it back down. Wipe it off and never see it again unless I do the same again. (Learned this from one of our engine builders on here)
So useing either seal can be of personal preference, and or which installation will be easier. Either seal can leak if not done right.
(Post # 10 in this "sticky" )
https://www.forbbodiesonly.com/mopa...-thread-on-rear-main-seal-replacement.127618/
Yeah, I'm old school and believe in "if it ain't broke, why fix it?" The only thing about the rope seal is that it can dry out if the engine sits for long periods of time. (New ones are not made of the same material as the original ones either. Thank you EPA) Some actually leaked from the factory. The Viton seal won't, or doesn't suppose to, dry out, and was the main reason that it was created.
Either seal, if not correctly installed, can leak. Over pressure of the crankcase will push oil past either one. If the split seal is installed backwards, it's guaranteed to leak. I'm not crazy about silicone sealer and would use Permatex #2 instead. The placement of the cap is of the utmost importance. As shown in the instructions of the Viton seal, careful measurements that are transferred from the block to the retainer and the centering, will insure proper retainer placement when installed. I've had good luck so far with the Viton seal and the side seals.
The leak that I do have is from not applying any sealer in the recessed cap bolt holes. Some pan gaskets don't completely cover this area and oil can make it's way past the gasket. It only leaks after I jack the front of the car up for a period of time then let it back down. Wipe it off and never see it again unless I do the same again. (Learned this from one of our engine builders on here)
So useing either seal can be of personal preference, and or which installation will be easier. Either seal can leak if not done right.
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IQ52
Well-Known Member
I'd be curious to know what ring pack you are using and what are the rings gaped at.
72golddustermike
Well-Known Member
Mahle rings not sure in gap.
lewtot184
Well-Known Member
I believe it has been proven that the lip on the neoprene seal doesn't ride on the knurl. it's contact point is to the inside of the knurl. if the seal is in backwards that's another issue. if the seal is leaking quarts i'd think the underside of the car would be pretty messy.
IQ52
Well-Known Member
Then I would put a blow-by meter on that rascal and start running the rpm's up.
Oval the retainer holes side to side. Don't use side seals. Let the seal center the retainer. The retainer may be located off center.
Doug
Doug
72golddustermike
Well-Known Member
Wherebu get one of those
72golddustermike
Well-Known Member
Did not oval retainer. I did not use side seal used ultra black and pipe cleaner for side seals.
Challenger340
Well-Known Member
It takes one helluva lot of blowby to cause Oil to be pushed out a rear main seal, especially if you already have a PCV and Breather which are easier paths for the gases.
In my experience only....
Probably NOT the Seal
Probably NOT the Crank surface
nor
the seal retainer....
Crank surface...
yada...
yada....
And my questions would be:
1.) have you checked how far OFF your Rear Main Seal Groove is to the passenger side in your particular Block from the Crank centerline ?
All Blocks exhibit this OFFSET to at least some degree, some are just worse than others, causing the Seal to be barely touching/sealing on the Crank in some Blocks if the Seal is just "placed" in the groove and the Crank plunked down with NO seal adjustment.
and,
2.) Have you read the following thread on Rear main Seals explaining the Block condition described above in #1, and how to check/repair it ?
https://www.forbbodiesonly.com/mopa...-thread-on-rear-main-seal-replacement.127618/
In my experience only....
Probably NOT the Seal
Probably NOT the Crank surface
nor
the seal retainer....
Crank surface...
yada...
yada....
And my questions would be:
1.) have you checked how far OFF your Rear Main Seal Groove is to the passenger side in your particular Block from the Crank centerline ?
All Blocks exhibit this OFFSET to at least some degree, some are just worse than others, causing the Seal to be barely touching/sealing on the Crank in some Blocks if the Seal is just "placed" in the groove and the Crank plunked down with NO seal adjustment.
and,
2.) Have you read the following thread on Rear main Seals explaining the Block condition described above in #1, and how to check/repair it ?
https://www.forbbodiesonly.com/mopa...-thread-on-rear-main-seal-replacement.127618/
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Hemirunner
Well-Known Member
Jegs has one that’s affordable
Another reason for a rope seal. MO.
Hemirunner
Well-Known Member
Unless the seal got put in backwards, or they used one of the crappy, undersize FelPros, I see this being something else. Upside down rings (I’ve seen it!) or excessive blow by pushing out the back of the intake manifold or something strange like that.
I have pictures somewhere of the newer FelPro seals next to a high quality viton. They’re considerably smaller than the high dollar viton seals. The local guy here used one and it made a mess all over the dyno. Changed to a viton seal and problem solved.
I have pictures somewhere of the newer FelPro seals next to a high quality viton. They’re considerably smaller than the high dollar viton seals. The local guy here used one and it made a mess all over the dyno. Changed to a viton seal and problem solved.
Garys1969RR
Well-Known Member
Good point. It has been observed that some big bore motors can get ring flutter above 3500 RPM, causing excessive blow by. So you set the 2nd ring end gap at .025 to .026, to reduce the ring flutter. That's what I did on the 512 in building.
My 496 had so much blow by that it was forcing oil out some of the seals and gaskets, mainly at the front of the motor. This was always seen after a full throttle pass at 6500 to 7000 RPM. SO ADD some crankcase venting, and check for excessive blow by past the rings. Strangely, there was no sign of the rear seal leaking on this motor, only up front.
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