Rear main seal orientation for 331 engine

[Bob Kielar]

Having trouble getting the rear main seal not to leak on my 1955 Cadillac 331 engine. Is this the correct way to install with the lip facing the engine?

Thanks,
Bob Kielar

[Dave Shepherd]

Yes, lip faces forward.  If the journal is knurled, as some were with a rope seal. That can cause issues with a modern seal.

[walt chomosh #23510]

Bob,
  If your having issues and are changing seals W/O success, it is possible that your crankcase pressure is too high resulting in leaks.And, in regards to the "modern" seal, it is made in such a manner that the crankcase pressure applies pressure to the seal pressing against the crankshaft. Also, sealant should be applied to the edges where the seal butts together. (minimal amount) Good luck sealing up your 331! ....walt...tulsa,ok...ps. A "high level" restoration shop in Tulsa once had a Cadillac from the 30s that had no rear seal. So they believed this was incorrect and thus had a VERY high level machine shop machine a seal. This resulted in LEAK city!So they removed the seal and guess what.....no leaks!....

[V63]

I just put in one of those replacement lip seals into a 1961 Chevrolet truck 6 cyl.

It was obvious the engine hemorrhaged oil before with the original rope seal design that was a 'replacement'.

My engine was in the vehicle and I worked from underneath. I loosened the crank mains and let the crank drop  1/16 of an inch. It was a significant effort to push  the upper seal 1/2 around the crank. I used no sealer on it and I left the seal at 10:30 and 4:30 so its ends did not meet with bearing cap. I put a dot of quality RTV on each end. I Did use RTV on the entire lower groove. I cannot report success "yet" ...hope springs eternal.

As for rope seals my 'understanding' is modern replacements are extremely lacking vs original manufactured ones, moreover they originally had asbestos construction.

It did read in my instructions there could be leakage due to 'break in' of seal but my read there was a drip or two.

Since your car has a road draft tube it seems unlikely excessive pressure would be at issue.

[Jay Friedman]

If anyone is interested, I can email an article written by my friend Art Gardner with a step by step procedure for installing a modern neoprene seal in a 331 engine. Email me at jaysfriedman(at)yahoo.com and I'll reply with the article. 

[Joe Jensen]

Bob:

Felpro has instructions on their web site for a two piece seal install:  https://www.felpro.com/technical/tecblogs/how-to-install-rear-main-seal.html

I had issues with the first rubber seal I put in my 331.  I did it a second time recently following the instructions on the Felpro site and so far so good.

Good luck!
Joe

[Caddy Wizard]

Having trouble getting the rear main seal not to leak on my 1955 Cadillac 331 engine. Is this the correct way to install with the lip facing the engine?

Thanks,
Bob Kielar

Please post clearer pictures of this.  I can't tell from the pictures which direction the lip is pointing...

Art G

[Roger Zimmermann]

Art, if you open the link supplied by Joe, you will see the direction of the seal.

[Caddy Wizard]

Art, if you open the link supplied by Joe, you will see the direction of the seal.

I am familiar with how to install these.  I couldn't tell from Bob's pictures how they had installed them in his engine (correctly or incorrectly)...

[Bob Kielar]

They installed it lip toward engine.

Bob Kielar

[Caddy Wizard]

They installed it lip toward engine.

Bob Kielar

Hmm...  well, this is a mystery.  Is the crank journal where the seal rides nicely polished?  Some mechanics install such seals with the joint between the two halves mis-aligned with the mating surfaces of the bearing.  Personally, I don't think that would make much difference, but it is worth a try.  Some folks put a dab of RTV silicone sealant on the ends of the rubber seal where the two halves meet.

I would also look at how the pan gasket and cork rear main journal crush gasket engage with each other.  I wrote a tech article years ago about how to get this area of the pan gasket to seal 100% drip free.  I'll see if I can dig that up..

[Caddy Wizard]

Here is my tech article from 2008...

I hate an oil leak.  It is embarrassing, frustrating and just plain messy.  One of the worst oil leaks on a '49 Cadillac is the engine rear main bearing seal, a repair job that intimidates many owners.  I know, I suffered with this leak in my 55 Series 62 Sedan (with the same motor) for about 12 years because I didn't want to take the engine out, but replacing the rear main seal CAN be done correctly with the engine in the car. 

The engine in my '49 6107 Club Coupe was carefully rebuilt recently with the installation of a Teflon-impregnated rope rear seal, which after 500 miles started to leak.  The oil pan also seemed to be leaking for two additional reasons: 1. the bolts were slightly loose, which typically occurs after the engine is put back in service and the engine heat shrinks the gasket; 2. the rear pan gasket had been made out of silicon liquid instead of the original cork strip, and it came apart.  I repaired everything without removing the motor and it seems to be holding perfectly -- no more drips on the driveway!  So here is my recommendation on how to proceed:
   
1. Buy a neoprene (rubber) seal from Terrill Machine in Deleon TX, Olson's Gaskets in WA or from one of several other Cadillac parts vendors that sell them.  Do NOT use a rope seal.  Some guys are good at installing the rope seal, but the installation and trimming of the rope to just the right length is CRITICAL.  Instead, the modern-style rubber seal provides a true dynamic lip seal and the installation is more idiot-proof.  Also buy a quality oil pan gasket set.  I like the "BEST" brand for these types of parts instead of FELPRO.  Olson's carries them.

2. Drain the oil, then use a lift or jack the front of the car up relatively high, preferably putting the front wheels on ramps (be sure to chock the rear wheels or put the rear of the car on jack stands);

 3. Remove the 2 bolts in the frame holding the idler arm on the passenger's side of the steering links and lower the center link.  Remove the exhaust crossover pipe;
     
4. Disconnect the battery ground cable and remove the starter (heavy!).  To do this, unscrew both of the small wires that attach to the solenoid, noting which one connects to which terminal.  Place a rag on the frame rail and rest the starter on it.  The positive cable will hold it there satisfactorily, so there is no need to undo any of the other wires;
 
5. Remove the oil pan and the lower flywheel cover (heavy) to provide working room to get at the seal.  Inspect and repair any "dished" bolt holes in the pan -- the oil pan surface should be flat.  Often, when an oil pan or valve cover is leaking, some ham-fisted mechanic or owner will over-tighten the bolts trying to stop the leak.  This deforms the pan or valve cover and ensures that it will leak from now on.  If need be, hammer the bolt holes flat with a small hammer and a narrow block of wood to act as an anvil.  Re-check for flatness.  Use a long, STRAIGHT board with a long piece of sand paper to flatten and re-surface the bolt pattern surface, if desired.;

6. Remove the windage pan, the tray-like baffle bolted to the bottom of the block and the oil pump;

7. Remove the rear main bearing cap.  Remove or, better yet, just loosen the 3 middle main bearing caps, leaving the front one alone.   (Note the direction the middle bearing caps face if you remove them, as it is important to replace them in exactly the same position.)  You do this to let the crankshaft droop just a fraction of an inch or so to slightly free up the upper half of the rear main seal;

8.  Screw a slender wood screw into one end of the upper half of the rope seal and grab the screw with pliers.  Using a brass, wooden or plastic rod (in order to not scratch the crankshaft journal), push up on the other side of the upper half of the existing rear main seal, while pulling down on the pliers to draw the rope seal out of the crankshaft journal.  Once it protrudes out a bit, you can grab the seal itself and pull it with the pliers. 
 
9.  Installation of the rubber seal requires no tools -- just slip it into place in the upper half.  NOTE: the direction/orientation of the new rubber seal is critical. Follow the directions on this that come with the seal. 

10.  Install the cork strip in the groove/channel in the rear main cap and trim to length, as shown below.  Trim it so that the ends of the cork slightly protrude from the end of the cap in such a way that the ends of the cork strip are parallel to the ends of the cap.  You want the cork gasket to have some "crush" to it when the oil pan is bolted up.  This is much easier to trim before installing the cap (otherwise, substantial trial and error is required).  Although probably unneeded, you can place a small amount of silicone gasket sealant on the end of the cork strip immediately prior to final fitment of the rear main bearing cap against the block (before the silicon has a chance to set).  Place the lower half of the rubber rear main seal in the rear main bearing cap and orient it according to the instructions;
    

11. After coating the lower main bearing halves with oil, replace the main bearing cap(s), including the rear cap, and torque them according to the shop manual specifications.  Cleanliness is of paramount importance here.

[Bob Kielar]

Yes the crank journals are clean. I was at the shop yesterday and gave him a print out of Arts rear main install procedure. He tried a rope seal and that leaked also. So he has another seal that came with the cam and crank kit. He doesn't know the brand it came from the engine machine shop. It looks like  it has a double lip and not as pliable as a best gasket it's brown in color. Wish I would have taken a picture. They are not charging us for any labor to get the engine running correctly and leak free.
Thanks for all the replies.
Stay tuned,
Bob Kielar

[Daryl Chesterman]

I don't know how other brands of rear main seals are made, but the Fel-Pro seal has a small raised ridge on the back side of the seal and if the installer does not use the "shoe horn" supplied, to install the upper half (if one is not supplied, the installer has to make one) that small raised ridge will get peeled off, with the result being there is not enough pressure applied to the seal lip and the seal will leak—Been there done that!!!

From the Fel-Pro instructions on the link that Joe Jensen supplied in post #5:

     The upper portion can be slid into place around the crankshaft. A shoehorn tool is provided to help prevent damaging the back side of the seal as you insert it.

Daryl Chesterman

[Omarine]

For what it's worth, i just replaced rear main seal on chevy 348. I used best gasket and followed instructions to a tee which included drilling a small post into the cap to anchor the bottom half of the seal as well .003" protrusion at the block surface. Seal was lubed and used some differential sealant around mating surfaces and pushed block half of seal deep into the groove with crank out.

Sealed up the oil pan and it's leak free 500 mi into the break in. Leaked like a civ before.

[Bob Kielar]

Had trouble getting the rear main seal not to leak used a best gasket with some sealer that leaked, took apart and replaced with a rope seal that leaked.  The mechanic then used the brown seal that came with the kit from rebuilders choice that the machine shop purchased. This is how he installed it. I sealed the underside with right stuff on both halves, as I did with this seal. There seemed no leakage on underside. As the same on rope seal, I did NOT use sealer on rope seal. He also stated it was a tighter fit. No leaks so far.

Regards,
Bob

[Paul J]

I used the terill seal also several times, but always was the result a leak..
Last two times I repaired a 331 cadillac engine I used the Felpro BS40245 seal.
You just have to cut the two wings off.
That seal feels a lot better ( tighter) when you put it in.
No leaks so far, and one I drove 7000 miles already.
The BS40245 seal is from the small block Mopar engine.

Kind regards, Paul,  an old mechanic from the Netherlands

[Chopper1942]

If a rope seal is correctly installed, they do not leak.  The problem is the seal is not prepped before installation.  I always had a seal set for engine I worked on in a can of oil.  At least a week and sometimes months.  This allows the rope to adsorb the oil and not burn on startup.  If you loosen the main caps to allow the crank to lower slightly, it is much easier to install the upper seal. You need a Chinese finger trap tool to pull the seal around the crank. Torque the other main caps to specs. Cut the seal off flush with the block.  Install the lower rope in the cap and use a hammer handle to press the rope into its groove. cut off excess flush with the cap, and clean all the oil off the cap and block. Back in the day, I used a thin coating of Permatex 400 on the main cap but today put a thin coating of GMS on the cap surface and then install the cap and torque to specs.  If correctly installed, it will not leak.

[Caddy Wizard]

My 49 60S has a 52 drivetrain, rebuilt about 30 yrs ago (but few miles since then).  The rear main seal has been leaking and making me crazy, so I am re-doing it.  It turns out that they had installed a rope seal.  I am going back with a rubber seal (Best brand).  Here are some photos of how it fits in the bearing cap...

[Omarine]

Interesting. I could be wrong about caddy, but when i did this on a 348 chevy, the rope and neoprene seals were not interchangeable.

My rope seal stopped the leaking. It was imperative to roll the seal in and ensure it seats down as far as possible. Idea is to use a similarl diameter tool to roll over it in the block. Like pvc pipe. I found a spray paint can to be a suitable substitute.

Used sealant on all pan surfaces to include small pieces that go over the rear main cap, etc.