# rope seal/rear main



## maktope (May 22, 2013)

While my car is up on the lift we found where It is leaking a Lil oil. Mechanic said it's the rope seal Google search comes up rear main. Is there a way to change this without pulling the motor? Are there better options available for the seal.


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## maktope (May 22, 2013)

And if i do have to pull the motor. my next question is, ive been wanting to replace my cam with a bigger one. Currently i have a 283/303 .513/.498 comp roller. I would like a bit more lobe. But i dont want to go so big i loose drivability. Here are the stats on the motor. 434 Cu, #64 heads bored .030 still have 428 crank. above cam 1.5 rockers. Edelbrock performer rpm intake, thunder 800cfm carb. Hooker 1 5/8 tubes to 3 1/2 collectors. MSD ignition. Muncie M20 with 12 bolt 3.55 rear


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## Instg8ter (Sep 28, 2010)

can be done but its much easier with the motor out, If your gonna put a cam in i would just pull it and do both on the stand.


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## SCG Pontiac (Feb 23, 2014)

It is actually quicker to pull the engine out. While it is possible to change while in the car in fact they even make a special pointed tool to pull it out with the engine in the car. I promise you it will leak with the new retro fit seal. Better to spend a few extra hours doing it right than lots of hours doing it over. And yes there are Viton rubber seals that replace rope seals you can get them from several vendors. I use rope seals in every engine I build if installed correctly still the best seal available IMO


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## rexs73gto (Nov 25, 2012)

If you just want a bit more lobe , why not just change the rockers to the 1:65's & that will give you a little more lift & then you can see if you want or need to go bigger then that. Also I would pull the engine to install the rear main seal. I would go with the viton seal , it a rubber type of seal & if you put it in correctly it will never leak again plus it will not have as much drag as the rope seal. It won't be much difference but every little bit helps. I've put them in the last 15 engines I've built & have had no problems at all. they are a bit more expensive but well worth it. Plus now if you use the 1:65 rockers you will have a true 1:65 ratio & not just close as the stamped steal rockers from the factory ,,,, if you still have them in your car. The 1:65's will make a big difference in the pulling power in th e cam you have at present with them.


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## BearGFR (Aug 25, 2008)

Caution about 1.65's - it's not just a simple swap. If you're running factory cast iron D-port heads, just replacing the rockers will most likely result in the pushrods rubbing where they pass through the heads. Those holes will need to be elongated to provide clearance, and of course that means the heads have to come off so you can clean all the debris after grinding.

Also, rear seals in Pontiacs are one of the more difficult jobs to do and get them to seal. I put a Viton seal in my 461 and I guarantee you the directions were followed to the letter. Guess what? It leaks. Whenever I have a reason to pull the motor again I'm going to try a graphtite rope seal. My theory is that it's because the block has been align honed and that process leaves the seal groove slightly oval shaped.

Regardless - if you do the job with the engine out, then you have a chance to test it before you go through the trouble of reinstalling the engine. Fill it with oil and then support it so that it's tilted up enough in front to submerge the rear of the crank in oil. Let it sit like that for a day or two. You'll know then if it's sealed or not. Much better to find out and have a chance to correct it before you reinstall the engine.

Bear


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## Instg8ter (Sep 28, 2010)

Great tip Bear...we all hate doing things twice. I'm in the same boat and plan on the same course of action. I am accumulating any parts now that i will want to change next winter while i have the motor out (Sacrificial offering to Chief Pontiac for the new seal to take, RA manifolds, downtubes, X-pipe, 12 bolt 3:55 posi, and possibly an OD trans).


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## SCG Pontiac (Feb 23, 2014)

Good advice Bear! Those shiny aluminum 1.65 rockers look pretty cool in the catalog and after all they " Bolt right on". But the way they get the additional lift is by moving the fulcrum point on the rocker which pulls the vertical clearance on the pushrod into the head.
You don't even have to be a Pontiac expert to know that pushrods work much better when they are not grinding against the heads.

On the rear seal, I have seen both rubber and rope leak but just as many Viton leakers. We took a 400 apart last week that showed signs of the Viton seal being brittle from heat.

I promise you a zero leak seal if you follow this method. Take the graphite seal and force it down into the groove with your fingers. Then use the biggest impact socket you have to tap ( with a hammer) and roll the seal as flush as you can get it. Do the same for the cap and remove the seals before you cut them. Put some RTV in the groove and roll the seals back in. Let them set over-night. Cut the rope very straight at about .003 long on the block and the cap. Just before you lay the crank in the block oil the seal with engine oil NOT assembly lube. Now carefully push the ends of the rope just below flush on the block and cap. Use a small amount of RTV under the cap but avoid the end of the rope seal. DO NOT turn the crank until all caps are torqued.The ends of the seal with relax and push into each other forming a leak proof seal. Some say that the rope seal is out of date technology and they are right but guess what? So is the rest of your car including the block, crank and main bearing cap. The rope seal is right at home and perfect for the job. Also I really have noticed very little difference in the original asbestos seal and the replacement graphite when it comes to performance.


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## maktope (May 22, 2013)

This is a new one for me. Don't have much space to pull the engine at home. That's the main reason I haven't done the cam yet couldn't justify the expense. Well since the engine should be pulled to do it properly I will see if my buddy will "rent" me space and tools at his shop. I do have my wishlist for a rebuild and if the engines out all that's left is for the wife to say yes.


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## SCG Pontiac (Feb 23, 2014)

maktope
( all that's left is for the wife to say yes.)
Just remember its easier to beg for forgiveness than to ask for permission.


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## Koppster (Jul 27, 2008)

Probably old news to you guys but just in case, new one piece seal being manufactured:

New BOP One-Piece Rear Main Seal - PY Online Forums


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## BearGFR (Aug 25, 2008)

Wow, Koppster - thanks for the heads up on that. After reading about it and the installation instructions, I admit it sounds very promising.

Bear


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## Koppster (Jul 27, 2008)

Agree Bear, I'm hoping to hear some first hand experience on how well they work.


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## BearGFR (Aug 25, 2008)

I talked to Jim yesterday, and he's going to use one in a 389 build soon. He likes the idea of them too. We'll see how it goes.

Bear


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## geeteeohguy (Feb 2, 2008)

With no split parting line at the cap and dual seal lips, it _has _to be a lot less failure prone than any of the others. I don't see how it wouldn't work. I've had good 'luck' with the split Viton seal, but it may be just that, luck. As tough of a chore as this is, this seal sounds like the way to go.


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