# 68 Gto Rear Main Seal Leak



## khinton (Jun 22, 2008)

have a 68 gto, stock engine 400 with only a true 27,000 miles. engine is in great shape but the rear seal leaks..Looking for recomendations to fix the leak. Don't want to have to do work twice so I'm looking for advice.


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## 05GTO (Oct 6, 2004)

BOP Engineering has the best rear main seal for Pontiacs, I'll be changing my 67 in a few weeks.


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## 68greengoat (Sep 15, 2005)

I'll thank you for the advice too. I need to change my rear main in my '68. Although, it has a '73 455.


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## Koppster (Jul 27, 2008)

05GTO said:


> BOP Engineering has the best rear main seal for Pontiacs, I'll be changing my 67 in a few weeks.


Randy,

Please provide an after report, mine needs changing too.

I believe you told me it can be done with an engine "lift" vs "pull".

Rick


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## geeteeohguy (Feb 2, 2008)

The only right way to do it is to pull the motor and put it on a stand, upside down. Don't ask me how I know. Also, I've had good luck with the new Vitron seal on a couple of engines I've assembled. As for the rope seal in my own '67: it leaks, has leaked since 1989, and will continue to leak.....at least for now!!!


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## 05GTO (Oct 6, 2004)

Koppster said:


> Randy,
> 
> Please provide an after report, mine needs changing too.
> 
> ...


I'll be pulling the engine and taking pictures for the forum, I was mistaken when I said you could do it with a lift. I received the BOP Engineering seal Saturday.


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## 68greengoat (Sep 15, 2005)

geeteeohguy said:


> The only right way to do it is to pull the motor and put it on a stand, upside down. Don't ask me how I know. Also, I've had good luck with the new Vitron seal on a couple of engines I've assembled. As for the rope seal in my own '67: it leaks, has leaked since 1989, and will continue to leak.....at least for now!!!


BOP Engineering uses a Viton seal. I'm assuming that's what you meant as opposed to Vitron. Or, are they different seals?



05GTO said:


> I'll be pulling the engine and taking pictures for the forum, I was mistaken when I said you could do it with a lift. I received the BOP Engineering seal Saturday.


According to the intructions, it appears if you have a 421 - 455 motor the crankshaft needs to be removed to fill the anti rotation holes with high temp RTV sealer in the block and the cap. Motors under 421 only need to fill the holes in the cap? Looks like this process may be quite involved for my 455. But, probably have no other choice. Maybe that's why it wasn't fixed b/4 I got it......


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## khinton (Jun 22, 2008)

Randy ---I will be waiting for the pictures and any additional advice you may have --I have ordered the seal today


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## geeteeohguy (Feb 2, 2008)

Viton, Vitron, Tomato , Tomottow, yeah, that's what I meant. Funny, the rope seal in my '67 has leaked almost since day one, and it leaked before the rebuild, too. I almost suspect the directional oil grooves on the crank are cut in the wrong direction and are slinging oil outward instead of inward! I overhauled the 389 that's in my '65 in 1981, and it's never been apart since then, and it doesn't leak at all. Never has. Rope seal, too. Go figure.
Jeff


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## khinton (Jun 22, 2008)

any thing new I'm ready to begin to replace the main seal


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## 05GTO (Oct 6, 2004)

khinton said:


> any thing new I'm ready to begin to replace the main seal


I've had some other items keeping me busy, Maybe by the end of the month I'll be caught up with some other projects.


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## khinton (Jun 22, 2008)

I have had people tell me not to use the viton rubber seal but to use the best gasket graphite rope seal. they say the viton seal some times leaks bad but I have heard there is now such thing as any rope seal that does not leak. Help I'm about to replace the seal, the motor will be out tomorrow--which seal should I use --- I have them both but don't know which one to put in. Ken


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## 68greengoat (Sep 15, 2005)

I've heard the new rope seal is supposed to be good too. I saw an episode of My Classic Car, I believe it was, and they had a rep from Egge. He was praising the new rope seal. He also said how difficult it was to change the mindset of people who had the old style rope seal into believing how good the new one was. Maybe someone has used the new rope seal?


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## 68_Goat (Nov 7, 2008)

I installed a BOP rear main seal in my 400 when I built it, and it does not leak after 2K miles on it. I do agree that the only way to do it is to have the engine on a stand so you can do it right, and wouldn't even attempt to do it in the car due to the prep work to make the seal work right. Follow thier directions, make sure the seal surface on the crank is not grooved/damaged, and you'll be successful.


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## khinton (Jun 22, 2008)

Installed the Best Gasket graphite rope seal--it cuts off on the ends real smoth looks like a great improvement over the old rope seal; will see. Both cliff Ruggles an Don Johnson from DCI motorsports claim it to be more reliable than the Viton seal. Am waiting for the heads to be rebuilt then will reinstall the engine in the car. (Did a complete refresh) found one of the rod bearings with some copper showing so changed all the rod and main bearings --Crank Miked out perfect--lucky-- and pistons and rings were like new. The engine had been rebuilt by the previous owner; 20 over pistons and 10 under rod and main bearings. Problem was the rebuilder must not have cleaned the engine well when they did the rebuild because you could see the evidence in the rod bearings of grit. Too bad--all that work and money and very few miles and bearings shot. This time should do it!


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## geeteeohguy (Feb 2, 2008)

I read an article that shed some light on rope seals...I stated earlier that my 389 that I rebuilt in '81 has never leaked with it's rope seal, but the 400 I rebuilt in '88 has always leaked out of its rope seal. The article said that earlier rope seals contained a lot of asbestos fibers, for heat and wear quality (like brake shoes once did), but they REMOVED the asbestos, and the newer rope seals just didn't work well. Mine sure doesn't. I put vitron (SP?) newoprene seals in tow engines so far, and they have not leaked. They seem kind of cheesy and flimsy when they're in your hand, though. I don't know WHAT I'm gonna use when I pull the 400 back out of my '67 to releal the hemmorageing rear seal...


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## khinton (Jun 22, 2008)

Have you heard anything about the Best Gasket, brand graphite seal--It looks very subsatantial to me. I comes highly recomened to me by the guys mentioned above who tell me they have a lot of experience with it.--Ken


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