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Old 11-14-2018, 12:53 PM
#1965GTO #1965GTO is offline
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Default Drip drip rear main

#1 I hate oil leaks. During the rebuild of the engine for the GTO I installed a main seal from BOP. This bottom end is a 68 400. I cleaned and prepared as per the instructions. I used the gray high temp silicon as directed. I don't think it ever did seal. Now I have moved to warmer climate and don't have the engine lift or room to do it again. Years ago when I contacted BOP an engineer there told me, "nothing is perfect".
For the first time ever I had to add a quart of oil, VR-30, to bring it back to the full mark. There is only 400 to 500 miles on the last oil change Now the engine has maybe 10K on it and I get a several drops on the floor and the trans pan get coated. Is there any magic bullets out here short of pulling the motor to fix it???If I do end up doing it again what is the best rear main seal to use? I've been told the Ford 460 seal is the same. Fel-Pro always includes the fiberglass rope seal in the gasket sets that I have used. Repeat#1

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Old 11-14-2018, 01:07 PM
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Years ago over the period of a couple of years i pulled my engine a total of 5 times chasing an oil leak. I finally found it. See this thread here. http://forums.maxperformanceinc.com/...d.php?t=471237 As someone eventually pointed out, the shop manual instructs you to place a dab of sealant underneath that rear main. It never leaked again after that. There ended up being a small ''valley" in the block there from the machining process.

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Old 11-14-2018, 01:43 PM
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It is not the cheapest, simplest or most accepted fix, but a GZ vacuum pump took care of my leak that I had from day one on my street driven 469. Not a drop since the install in 2015. I will get flamed for proposing it, but it worked for me. End of story.

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Old 11-14-2018, 02:15 PM
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Quote:
Originally Posted by craigs69 View Post
It is not the cheapest, simplest or most accepted fix, but a GZ vacuum pump took care of my leak that I had from day one on my street driven 469. Not a drop since the install in 2015. I will get flamed for proposing it, but it worked for me. End of story.
There's no reason why building a vacuum in the crankcase should get you flamed. My preferred method for most gas engines is to seal the crankcase with the exception of one PCV valve to hook manifold vacuum to, resulting in a low pressure crankcase. This aids ring seal, helps eliminate small seeps, and reduces oil consumption overall. I run a catch can to trap nasty oil and moisture that I drain regularly.

Of course, this method works best on engines with lots of vacuum, but a vacuum pump is a great solution for a seriously cammed engine with low manifold vacuum.

Now having said all that, that's not the solution I would choose for a serious leak, or even as the primary solution to any seepage, but reality is that it will help, as you said.

The most common reason why rear main seals leak, in my experience, is improper installation or choosing the wrong seal. Fact is, neoprene rubber seals basically cannot seal properly on crankshafts with hash marks designed for rope seals. The only way to definitively get a neoprene rubber lip seal to work properly on such a crank is to have the sealing surface turned down smooth to remove those hash marks. This of course presents a problem, as the seals are designed for a given diameter sealing surface, so if you turn it down too far the seal still won't work. On Buick engines this is easy, as the guys have figured out a specific diameter to turn it down to and then a certain seal to use from a different engine that works great. Unfortunately I'm not aware of such a solution on Pontiac V8s.

I have installed many rope seals in many engines over the years, including Pontiacs, and they always seal for me, at least for a good amount of time. The seal I installed in my 212k mile 455 was still dry three years and 30k+ miles later when I pulled that engine.

The trick is to really pack it in the groove tight. I generally don't trim off much excess. I make sure the grooves in the cap and block are absolutely bone dry, I use a Q-tip or something to apply a THIN layer of GREY silicone to the inside surface of the grooves, then I pack the seal in dry. I let it cure for 24 hours. Then I smear a thin layer of grease on the rope and on the crank surface, bolt it all together and they just seal. Haven't had one fail on me yet using this method, again on Pontiacs and other engines.

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Old 11-14-2018, 03:50 PM
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Have you verified the crank seal itself is leaking or could the leak be from another source? If it actually is the main seal, you should see oil coming from the crank flange behind the seal and going down the flexplate/flywheel in sort-of a sunburst pattern. If the crank area is dry right up at the seal area, then it is likely the leak is elsewhere. Valve cover gaskets are a likely source where the oil will run down the back of the block, and the number two problem area is the pan gasket at the rear. Either of these two areas will mimic a seal leak, and sometimes it can be a real challenge to find the actual source.

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Old 11-14-2018, 04:20 PM
#1965GTO #1965GTO is offline
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Well fellas I guess I may rent and engine lift and engine stand this winter and try to do this again. I'm thinking I'll deglaze the cylinders and try Cleveite rings this time and a new set of bears too. There are King bearings and rings in it now. Might as well do it up right while it's apart. There are couple of good ole boys in the local car club that may have an idea or two on the rear main seal and be able to help me make up my mind. The question is to rope or not to rope. I do agree that the serrated crank groove was always been a concern for me too. I always thought it was an attempt to direct oil away from the seal area in the block and main cap.
I drove the car last Saturday to the VA hospital car show in Las Vegas. I'm running a 3.55 rear gear with a 200-4R transmission. I used 6.5 gallons of gas for the trip running 75-80 mph. The round trip was 145 miles so the tune is pretty good. I pulled the plugs yesterday just to look. AC 45s looked good after that run with just a little black on the threads. That's probably left from all the short runs around town. I'm also using the one piece pan gasket from BOP with great success so don't disregard them completely. A friend on mine here in town gave me a brand new water pump housing/timing cover last week, so maybe I'll get a chance to use it. I have checked the valve covers too and did find one little leak and went back with the rubber gaskets on the covers. The covers are the repoped Cal Custom finned aluminum and are straight and flat.


Last edited by #1965GTO; 11-14-2018 at 04:25 PM. Reason: more info
  #7  
Old 11-14-2018, 08:34 PM
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Half-Inch Stud Half-Inch Stud is offline
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got same drip, and it probably pour during certain driving events.
2 remedies in my mind for to do list;

1. install converter dust shield to funnel leak to ground.
2. GX vacuum pump

  #8  
Old 11-14-2018, 08:39 PM
tom s tom s is online now
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Is it the older 2 pc design or the newer 1 pc design?Over the years im 50/50 with the 2 pc and 100% with the one pc.Also 100% with the Best gasket rope seal.FWIW,Tom

  #9  
Old 11-14-2018, 08:51 PM
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Quote:
Originally Posted by Half-Inch Stud View Post
got same drip, and it probably pour during certain driving events.
2 remedies in my mind for to do list;

1. install converter dust shield to funnel leak to ground.
2. GX vacuum pump
HIS, I have always run a dust shield and the oil still managed to find it's way all over the underside of my car. The windage from the spinning converter caused it to end up in the starter and seep out around the parting line between the shield and transmission case. From there, the wind under the car deposited it on everything else. At one point, I actually used gasket sealer between the shield and case and velcroed an oil absorbent pad to the bottom of the shield to catch oil that dripped from the drain hole and, although better, still had a mess after each drive.

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Old 11-14-2018, 10:57 PM
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Half-Inch Stud Half-Inch Stud is offline
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My Starter is nearly dry.

My Oil adapter, Pass Collector, and Pass floor board back to the rear Housing are "rust-proofed" in oil glaze with soot.

So maybe one of us doesn't have a leaking Rear Main.

  #11  
Old 11-14-2018, 11:58 PM
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Fullsize455 Fullsize455 is offline
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Quote:
Originally Posted by tom s View Post
Is it the older 2 pc design or the newer 1 pc design?Over the years im 50/50 with the 2 pc and 100% with the one pc.Also 100% with the Best gasket rope seal.FWIW,Tom
No such thing as a one piece seal for a Pontiac V8. At least not for any stock blocks anyway, not sure about aftermarket.

  #12  
Old 11-15-2018, 12:00 AM
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Bruce Meyer Bruce Meyer is offline
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Whatever you do, don't use the fiberglass rope seal in the Fel Pro gasket set. They wont seal for long and they tear up the crank surface.

  #13  
Old 11-15-2018, 12:03 AM
tom s tom s is online now
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BOP makes a (1pc) seal for pontiacs!When you get it YOU make a cut to put it on the crank and drop It in the block.Do a search,BOP Engineering.Tom

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Old 11-15-2018, 12:06 AM
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Quote:
Originally Posted by tom s View Post
BOP makes a (1pc) seal for pontiacs!When you get it YOU make a cut to put it on the crank and drop It in the block.Do a search,BOP Engineering.Tom
What on earth would be the point of that? It may be manufactured as a one piece, but you cut it and now you have a seal with a split in it. I don't see that working any better than a traditional two piece seal.

A true one piece seal would be a major improvement, but of course would require a totally different crank and block.

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Old 11-15-2018, 12:14 AM
tom s tom s is online now
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Because it ONLY has one slit and IF you follow directions the seam is where it is designed NOT to leak!As said go to the site.There are lots of builders on this site that have used them succefully!I have put them in my last 4 engines with no leaks.Tom

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Old 11-15-2018, 01:43 AM
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Greg Reid Greg Reid is offline
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Quote:
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100% with the Best gasket rope seal.FWIW,Tom
I've had good results with that one also.. It's graphite and supposedly mimics the characteristics of the asbestos seals.
https://butlerperformance.com/i-2445...bga-6382s.html

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Last edited by Greg Reid; 11-15-2018 at 01:51 AM.
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Old 11-15-2018, 04:11 AM
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Just installed the BOP one piece on my recent build. Absolutely dry as a bone back there. Engine is still running on the test stand so it's easy to examine. I'm actually worried it's TOO dry. You can reach up and rub a finger along bottom of the seal/pan ... not even a mist of oil. And that's after I had the pan off three times. Also using a leak free BOP one piece oil pan gasket.

  #18  
Old 11-15-2018, 08:21 AM
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Quote:
Originally Posted by Fullsize455 View Post
What on earth would be the point of that? It may be manufactured as a one piece, but you cut it and now you have a seal with a split in it. I don't see that working any better than a traditional two piece seal.

A true one piece seal would be a major improvement, but of course would require a totally different crank and block.
Do some research. I never had a leak with the one piece seal. I even re used on and did not have a leak. I never had luck with a rope seal.

  #19  
Old 11-15-2018, 08:40 AM
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Quote:
Originally Posted by Half-Inch Stud View Post
My Starter is nearly dry.

My Oil adapter, Pass Collector, and Pass floor board back to the rear Housing are "rust-proofed" in oil glaze with soot.

So maybe one of us doesn't have a leaking Rear Main.
I bet your starter would be wet if you had a dust shield on.

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  #20  
Old 11-15-2018, 09:25 AM
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Half-Inch Stud Half-Inch Stud is offline
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Quote:
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I bet your starter would be wet if you had a dust shield on.

in the 1980's, i recall that was true.

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