# Opinions wanted on rear main seal(s)



## 2015xdrive (Sep 26, 2018)

Looking for guidance on new rear main seal for 66 389. Has anyone been successful in installing one piece Viton seal without completely removing the crankshaft? What experiences have you had with two piece Viton seal? And finally what experience have you had with new grafite rope seal? I have already committed to pulling the engine out and now need to replace seal. I would like to learn from others who have installed a new seal.


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## 1968gto421 (Mar 28, 2014)

I think member *BearGFR *has had real good success with rear main seals. You might want to either check out his posts or PM him for advice.


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## 2015xdrive (Sep 26, 2018)

Thanks! I will.
RC


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## Bluedog (Aug 8, 2018)

I tried to "roll" the one piece in with no success. Ended up pulling the crank. 
It seems to work great as I have not seen any oil drips. The one thing that was nerve racking was that when you place the crank back in you really can't see it seat on the seal. Just have to trust that it's straight.


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## BearGFR (Aug 25, 2008)

1968gto421 said:


> I think member *BearGFR *has had real good success with rear main seals. You might want to either check out his posts or PM him for advice.


I thought I did.... :frown3:

I put in a 1-piece on my recent rebuild, let it hang butt-down from the hoist with 2 gallons of oil in it for several days, and it was bone dry.

But now, after putting it in service and driving it..... it's not. dry. :crying:

In my particular case, considering that I used my hoist to install the seal and the crank and am dead positive I got it in right, my only explanation is that this new crank -- which has the serrations on the sealing surface -- damaged the seal due to the serrations now that the engine is running. Either that, or I'm an idiot and have no business building engines --- either possibility is valid. I still think the 1-piece seal is a very good solution, but if I decide to pull it and try again, the next time I'm going to give the graph-tite seal a shot. If your crank is smooth on the sealing surface and doesn't have the serrations, the 1-piece ought to work great.

Bear


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## geeteeohguy (Feb 2, 2008)

I've installed 4 of the BOP 2-piece Viton seals and one BOP Viton one piece seal. All engines were 389-400's, and all were running stock Pontiac crankshafts. Have had none of them leak. Oldest install is 12 years old, the most recent is 3 years old or so, the one-piece. The one in my own '67 is a 2 piece, with about 9 years of service and 10,000 miles. Bone dry. You DO have to pull the main caps and gently lift the rear of the crank up about a half inch to an inch....you do NOT need to remove the crankshaft. A helper is handy, or a cherry picker, as the crank is too heavy/awkward to hold with one hand while installing the seal. I 'clocked' the seals so that the seam would not line up with the cap and block seam...so it would be 'captured' by the block and cap. These seals LOOK very thin and flimsy and unsubstantial....but installed according to directions, they work great. I hear horror stories about these seals when used on the big journal engines, and sometimes with aftermarket cranks. The last thing you want with a big dollar build is a dripping engine.


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## BearGFR (Aug 25, 2008)

I talked to a buddy earlier this week about it, and other things. I've been a little "mad at" the car for awhile now and seriously doubting myself over it, which is one of the reasons I haven't been around here much lately. I figure if I can't get mine "right", the who am I to be giving advice?

Anyway, he mentioned something that I hadn't thought of... crankcase pressure. I'm running the factory style PCV, the factory style hard line vent from the passenger side valve cover to the rear of the air cleaner, and the factory style non-vented oil filler cap. My buddy tells me the combination of those two vents (PCV and hard line) won't be enough to vent the crank case pressure on a 461, so that could be what's causing my leakage - the pressure is pushing oil past the seal. That would at least explain why it was dry when I put it together but isn't after running. He says put a big breather on both sides. I reckon it's worth a try.

I'm also suspicious of another possible problem resulting from my ongoing battle with that @!#$%^&*() Holley that I **STILL** haven't been able to make behave how I want it to, but that's a topic for another day.

Bear


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## Lemans guy (Oct 14, 2014)

Bear, you may want to consider an ME Wagner dual flow PCV valve. You custom dial it in with a vacumn gauge. PCV valve have not changed in 60 years until the engineers at ME Wagner developed this one for hot Rodgers. That $5 PCV was not made for out 461 stroked motors.

I am running an ME Wagner valve and a radium catch can off the valve cover. The Wagner valve will pull 1 to 3 hg vacumn on your crankcase 99% of the time........no other PCV will do that. Relieving that pressure all th time will eliminate leaks from gaskets all around.

The key is you must use a baffled valve cover or baffled valley pan. The Wagner valve is so efficient it will pull too much oil vapor if it is not baffled.

Mine pulls one ounce of oil for each 1000 miles, a quart every 32,000 miles. Not much, but it captures all the blowby gases and condensation that destroy your engine and relieves the pressure at the same time. No more oil out your breathers on a hard run, all that pressure gets relieved.

Just open breathers will not create a vacumn, n old road draft tube created a slight vacumn at speed only and no relief at low speed or idle.

Check out ME Wagners website, a super nice billet aluminum well engineering piece that customs tunes you in. I highly recommend it.


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## the65gto (Oct 9, 2008)

I had an extra valve cover and installed it many years ago. Always thought that 2 was better than 1 :smile3:


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## Stereolab42 (Apr 6, 2018)

Second the ME Wagner. I use one on my Mopar. They have data on their website that demonstrates two open breathers is actually worse at reducing crankcase pressure than a typical stock PCV setup.


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