# Rear main seal replacement on 1981 Chevy 350



## steven1213 (Mar 1, 2008)

I have decided to replace all the seals on my 1881 Chevy 350 engine which are most likely to leak oil. The rear main seal looks as though it may be a bit of a pain since you have to fabricate a couple of tools to install it. The Chiltons manual says to "fabricate an installation tool out of .004" shim stock and shape the end to 1/2' long by 11/64' wide". This tool acts as a shoe horn. The other tool is a 1/2 " wood dowel with the end carved down to the size of the end of the seal to pack it in.
Does anyone know where I can get the "shim stock", and if there are any other things I should consider when installing the seal? I am still unsure how this fabricated shoe horn is supposed to look.-----Thanks for any help in this matter, Steve


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## wirenut (Jan 16, 2004)

i want to say once you get the old one out its not to difficult
to replace...if my memory servs me rite...


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## derekbroerse (Mar 6, 2004)

Alot of those aftermarket seals come with a little plastic shoehorn....


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## B&B (Nov 4, 2006)

Steve maybe you should have simply started a single thread on "How to reseal my small block Chevy". 


Derek's right on the money, most of the main seals do include the shoehorn...and they're just a piece of plastic, nothing special. The "shoe horn" is only used to protect the backside of the block half of the seal as you roll it into place in the block, since theirs a sharp edge on the block to main cap parting line. If you attempted to roll the seal in without the protection of the shoehorn, you risk shaving rubber of the back side of the main seal. Nothing fancy about this "tool". See below for a pic of the seal in a main seal kit. It's the blue part in the kit. I've made them from a plastic soda bottle before in a pinch.

You don't need a special "packing tool" either to finish the seal install, if you oil the backside of the seal before you install it, you should be able to push the seal all the way in with your thumb. If you need that last little bit to get it all the way around the crank and fully into the seal cavity, simply use any small piece of wood to push it the rest of the way in until it's level with the main cap surface. I use a wooden ruler cut in half.


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## derekbroerse (Mar 6, 2004)

Some people like to leave the seal sticking up slightly on one side (and therefore down slightly on the other, like 1/4") and mirror it in the main cap. In other words, rotate the seal like 15* in the block from its stock position. This moves the parting line of the seal away from the parting line of the cap/block, and is supposed to help prevent future leaks. 

Honestly, I've never tried it and have no idea if it works or not.

But a first time installer should PROBABLY just do it the stock way.


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## B&B (Nov 4, 2006)

derekbroerse;543724 said:


> Some people like to leave the seal sticking up slightly on one side (and therefore down slightly on the other, like 1/4") and mirror it in the main cap. In other words, rotate the seal like 15* in the block from its stock position. This moves the parting line of the seal away from the parting line of the cap/block, and is supposed to help prevent future leaks.


 I did many of them that way Derek, never found any difference between it and the standard procedure of setting the seal flush. For a newbie it's much more important just to be sure your installing the seal in the _correct orientation _rather than reinventing the wheel....

Install it with the lip facing the wrong way and she'll be an oil gusher for sure. :crying:


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## derekbroerse (Mar 6, 2004)

B&B;543728 said:


> I did many of them that way Derek, never found any difference between it and the standard procedure of setting the seal flush. For a newbie it's much more important just to be sure your installing the seal in the _correct orientation _rather than reinventing the wheel....
> 
> Install it with the lip facing the wrong way and she'll be an oil gusher for sure. :crying:


Absolutely.


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## steven1213 (Mar 1, 2008)

Thanks for the help guys. When I originally bought this motor I just intended on dropping it in the truck but 
figured I might as well do it right. I guess I should have titled the thread "Re-seal my 350"!
While I am posting I might as well ask about another problem. I broke the head off the 9/16" bolt which holds on the housing that the radiator hose mounts to, on top of the manifold. Any suggestions on how to go about fixing it? What size easy out should I use to extract it and about what size drill bit would work best for the easy out? Thanks again guys. ----Steve


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## derekbroerse (Mar 6, 2004)

steven1213;544131 said:


> Thanks for the help guys. When I originally bought this motor I just intended on dropping it in the truck but
> figured I might as well do it right. I guess I should have titled the thread "Re-seal my 350"!
> While I am posting I might as well ask about another problem. I broke the head off the 9/16" bolt which holds on the housing that the radiator hose mounts to, on top of the manifold. Any suggestions on how to go about fixing it? What size easy out should I use to extract it and about what size drill bit would work best for the easy out? Thanks again guys. ----Steve


Well, technically, you need an understanding of bolt sizes first so you can buy replacement parts and people will know what you are talking about. The bolt you are referring to is a 3/8" bolt, which has a 3/8" diameter shaft and takes a 9/16" socket. If you walk into a store and ask for a 9/16" bolt, they either won't have anything that large or will bring you a very large bolt. Bolts are always sized by the shaft diameter, not the head size.

The housing you are referring to is called a thermostat housing.

If you aren't familiar with drilling and using easy outs you can destroy the manifold pretty easily. You need to be right centered and straight. Start with a pilot hole, about 1/8" in diameter. You can probably work your way up to a 1/4" diameter hole or so. Oil it with penetrating oil first and let it soak!

Is this a cast iron stock manifold? Aluminum? Something aftermarket? 2bbl/4bbl? Is this maybe a good excuse to upgrade to something nice and inexpensive, such as an Edelbrock Performer intake? If you had to pay someone to remove this for you, you'd probably be ahead of the game to buy another manifold. Stock iron ones are basically worthless and people will give them away (I threw out 6 last year and still have a couple) or sell them real cheap.... but a Performer is only about $100 brand new, half of that used on ebay.

Just something to think about.


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## steven1213 (Mar 1, 2008)

I must admit I am not very good about knowing the thread size on bolts so the only way I could have identified it was on the socket size. I guess I should have distinguished that. Have any of you heard of heating it up with a torch and using candle wax to help lubricate the thread? I was told you heat the area enough to melt the wax and touch it against the base of the broken off bolt then use vicegrips on what is left of the bolt and loosen the bolt while it is still warm. I probably have about 1/2 to 5/8' left to grab onto which is pretty minimal.


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## B&B (Nov 4, 2006)

I have used the candle wax trick before with success. But it does seem to work better on pipe threads rather than a broken bolt. Pipe threads have much more clearance in their threads for the thick candle wax to flow into.

In your case you have plenty of bolt left to drop a nut down over and weld the nut to the bolt in order to back it out. 

A much more successful way to remove a broken bolt in my experiences.


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## derekbroerse (Mar 6, 2004)

Definately. I assumed you meant broken off flush.

Thread (if possible, otherwise slide a slightly larger nut over it) a nut onto the stub and weld it securely in place to the broken stub. You can even try the wax method here, but oil works well too (smokey tho). The heat from the weld tends to expand the steel of the bolt at a different rate than the manifold, thereby breaking the lock between them. Usually you can back the broken bolt right out. Might take a few attempts, depending on size and weld strength. Worst case you can always grind it and do the easy out method.... which I hate. Much prefer this method.


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## Cooter24 (Nov 13, 2007)

A dab of silicone on the seal ends will prevent them from leaking. Just a dab as too much would squeeze out and end up in the oil pan. Might as well pull the engine out and rebuild the entire thing.


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## wirenut (Jan 16, 2004)

it's most likley a 3/8-16x11/2
if you rap it a few times while turning with vice grips it will come out
(if its alum dont rap as hard) neversieze when reinstalling


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