Rear Main Seals
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Senior User
Joined: Feb 2009
Posts: 316
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From: Ridgefield, Washington
Rear Main Seals
Replacement of the rear main seals; is this a job that should only be done by a shop or can an amateur do it anticipated good results?
Engine is 239 V8 from my '55. Engine is out and on a stand. Clutch components are removed.
Also, any debate about rope type seals vs. neoprene?
I have some mechanical abilities but no recent experience. The last work I remember doing inside and engine was in 1965 on my 55 Ford car. My brother and I changed the connecting rod bearings without removing the engine, without checking the crank for needed repairs and without Dad's permission. Bearings lasted nearly a week!
Maybe I just answered my own question.
Engine is 239 V8 from my '55. Engine is out and on a stand. Clutch components are removed.
Also, any debate about rope type seals vs. neoprene?
I have some mechanical abilities but no recent experience. The last work I remember doing inside and engine was in 1965 on my 55 Ford car. My brother and I changed the connecting rod bearings without removing the engine, without checking the crank for needed repairs and without Dad's permission. Bearings lasted nearly a week!
Maybe I just answered my own question.
Are we there yet?
Joined: Mar 2006
Posts: 1,098
Likes: 64
From: NW Valley AZ
I am very interested in the response to this question. I have a 429 that needs the rear main seal replaced.
There are videos on you tube of people changing them without removing the motor and it seems like it can be done. Just have to have enough room to get the pan off.
If you already have the motor out you should be able to do it pretty easily.
There are videos on you tube of people changing them without removing the motor and it seems like it can be done. Just have to have enough room to get the pan off.
If you already have the motor out you should be able to do it pretty easily.
Fleet Owner
Joined: Jul 2004
Posts: 27,305
Likes: 1,062
From: NM
Unless you pull out the crankshaft (and therefore, all the rods and pistons), you can only do the lower half of the seal. I don't know if there is a neoprene seal option for Y-blocks or the 429's that doesn't require machine work, John Mummert's site would have them if there is one.
Getting rope seals installed isn't rocket science but results vary. I would for sure replace the lowers any time the engine is out and it's easy to pull the pan, for that matter pulling the pan is always worthwhile. I'd check a couple of main and rod bearings, note their sizes (marked on shells), possibly replace the oil pump too. Clean any sludge out of the pan.
Getting rope seals installed isn't rocket science but results vary. I would for sure replace the lowers any time the engine is out and it's easy to pull the pan, for that matter pulling the pan is always worthwhile. I'd check a couple of main and rod bearings, note their sizes (marked on shells), possibly replace the oil pump too. Clean any sludge out of the pan.
More Turbo
Joined: Jun 2003
Posts: 687
Likes: 80
You shouldn't have to remove rod/pistons. If you remove the main caps, you can slip the old upper half out and slide in the new one. Then you can set the lower seal in the retainer with the side seals. Make sure the mating surfaces for the lower retainer are very clean and dry, and put a tiny dab of RTV there before you torque it down. Inspect the retainer carefully to sure it's not warped. If it is contact John Mummert for a replacement.
Fleet Owner
Joined: Jul 2004
Posts: 27,305
Likes: 1,062
From: NM
Unless the Y-blocks are real different than flatheads and other engines I've done, the upper rope seal isn't going to slide in or out. If it could, it wouldn't seal worth a darn. If you can raise the crank up enough with the rods attached, and figure a way to hold it, that would possibly work, but I don't see how you'd roll it into the groove fully.
Logistics Pro
Joined: Dec 2005
Posts: 4,644
Likes: 55
From: Moro Bay, AR
I've done several rope seals in the vehicle where I force the old seal farther into the upper groove on both sides with a punch and then drive a short piece into the opening to take up the space. Put the lower seal in as usual and reinstall bearing cap. Never had one leak doing it this way. An older fellow showed me this many years ago.
FTE Legend
Joined: Sep 2003
Posts: 54,132
Likes: 2,454
From: NY and VA
Easy enough to do without pulling crank. Seal cap off, punch some on one side of the seal in block, sheet metal screw into the other end of seal. Pull on screw enough to expose one end of the seal so you can grip it with pliers to pull out. It helps to turn the engine as you pull on the seal. Installing - make sure the seal is really soaked in oil first. There are kits available. For example:
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Logistics Pro
Joined: Nov 2011
Posts: 4,685
Likes: 81
From: Northville, MI
Unless you pull out the crankshaft (and therefore, all the rods and pistons), you can only do the lower half of the seal.
Getting rope seals installed isn't rocket science but results vary. I would for sure replace the lowers any time the engine is out and it's easy to pull the pan, for that matter pulling the pan is always worthwhile. I'd check a couple of main and rod bearings, note their sizes (marked on shells), possibly replace the oil pump too. Clean any sludge out of the pan.
Getting rope seals installed isn't rocket science but results vary. I would for sure replace the lowers any time the engine is out and it's easy to pull the pan, for that matter pulling the pan is always worthwhile. I'd check a couple of main and rod bearings, note their sizes (marked on shells), possibly replace the oil pump too. Clean any sludge out of the pan.
Don't ask me how long it took me to do it the first time until someone clued me in on bumping the starter.
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Senior User
Joined: Aug 2013
Posts: 355
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From: Peoria IL
Does no one own the right tool for the job?
The tool is called a sneaky pete - its a wire corkscrew looking tool that you twist into the rope seal in the top.
Drop the pan, pull the end cap & twist the sneaky pete (costs like $10) into the upper rope seal.
Pull it out.
Use a new neoprene 2 piece seal.
No joke here - make sure you have the new seal oriented correctly - there is a front & a back.
push the new upper half into the upper groove. Off set this seal about 1/4 inch. don't line it up with the cap - you want 1 end pushed in some & the other end sticking out some.
Use high temp RTV & put a blob on each end of the seal.
Put the second half in the rod cap you pulled & put the cap back in place - torque to spec.
new pan seal & you are done.
I've done this on an old 58 chevy stovebolt -- I was shocked at how easy it was - & the new type of seal will not leak!
Get the right tool though - check amazon, or online -they are everywhere.
The tool is called a sneaky pete - its a wire corkscrew looking tool that you twist into the rope seal in the top.
Drop the pan, pull the end cap & twist the sneaky pete (costs like $10) into the upper rope seal.
Pull it out.
Use a new neoprene 2 piece seal.
No joke here - make sure you have the new seal oriented correctly - there is a front & a back.
push the new upper half into the upper groove. Off set this seal about 1/4 inch. don't line it up with the cap - you want 1 end pushed in some & the other end sticking out some.
Use high temp RTV & put a blob on each end of the seal.
Put the second half in the rod cap you pulled & put the cap back in place - torque to spec.
new pan seal & you are done.
I've done this on an old 58 chevy stovebolt -- I was shocked at how easy it was - & the new type of seal will not leak!
Get the right tool though - check amazon, or online -they are everywhere.
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