Rear Main Seal installation on split case

[4kidsno911]

Hey Pelicans,

Was wondering if some of the more experienced engine builders out there can chime in on on position for the main seal when mating the two case halves. I found many threads on replacing with the engine together but nothing on correct location with engine apart. Mine went on very easily and before I close the case I wanted to ask on this. In the pic I have it just proud of the case surface which was how it was before rebuild.

thanks, Brian

[gled49]

I tap it in flush in the final stages of closing the case.

[4kidsno911]

Thank you

[Henry Schmidt]

If your plan is to "tap" the seal into it's final position, I would suggest a few dabs of Bosch grease on the inside of the seal to insure that the spring does not jump out from the impact.

[4kidsno911]

Thank you Henry,

I am concluding that if possible, considering time constraints you would get it flush with the case all the way around before final torque of the case half’s.

[Swann]

Hey Brian,
You're on the right track checking this before sealing it up. When assembling the case halves, the main seal should typically sit just slightly proud of the case surface, flush to 1 mm proud is generally considered safe.

[4kidsno911]

Thank you for the response. Super excited to close the case and start building the long block.

[Jeff Alton]

We NEVER attempt to install the RMS while assembling the case. Just use the correct tool after assembly which assures the correct depth and seamless/faultless install.

"Just proud" and "flush" are not the correct positions.....

Cheers

[Henry Schmidt]

We have the factory tool and still, we ALWAYS install the seal as part of the case assembly process. Any time you press a seal in you risk damage due to unequal pressures that can distort the seal. You also distort the perimeter of the seal where you will find small ribs designed to seal without sealant.
The factory tool can be a life saver after the fact but not my first choice.

[JoeMag]

Another thing to check is the sealing surface on the case has not "developed" any scratches. Can happen by rough removing of RMS. ...mine has, 993Cup case that probably saw many rebuilds before I got it. I need to use sealant.

Here's install depth of RMS. ...at least according to 993 manual.

[Henry Schmidt]

Given the age of these old motors and the wear you can see on the cranks, check for any groove that may have formed in the flange over the years.
You can grind the crank if it's not too deep (too much and the seal tension might be inadequate) or install a Redi-sleeve.
If you find yourself in a position where a grooved crank is inevitable, you want to install the new seal so that to sealing lip/surface coincides with a clean portion of the crank flange. A few thousandths either way could mean the difference between success and dropping the engine one more time.

[dannobee]

I'm with Henry on this one. I've always put the seal on the crank during final assembly with just a smidge of sealant along the case parting line. You can easily double check the garter spring and eliminate any chance of seal damage that can happen when using the special tool.

[4kidsno911]

Thank you for all the info on this.

[Old H2S]

Go look up my old thread on installing 3 RMS's.. Getting A good RMS that is a tight fit is the first thing to do. If upon closing up the case you can push the seal in with just 2 thumbs the seal is too small and will leak. Elring seals were too small and I proved it with non contact video inspection measurement tools that showed a -.010" OD mistake from the manufacturer. Has it been corrected? A bad lot? Different factories? Counterfeit parts? I do not know..
The Cortico seal fit nice and tight.

[stubble88]

Mine now sits cockeyed by doing it this way. Now I need to re-do it. Maybe just do it after closing.

[PeteKz]

With respect to the pros who install the RMS while closing the case halves, I have done it by installing the seal after the case has been put together. I just tap the seal into the bore with light even taps all the way around. No leaks.

After all, if you have to replace the RMS at some point many years down the road, would you split the case to replace the seal?

I didn't think so.

[Henry Schmidt]

Originally Posted by PeteKz

With respect to the pros who install the RMS while closing the case halves, I have done it by installing the seal after the case has been put together. I just tap the seal into the bore with light even taps all the way around. No leaks.

After all, if you have to replace the RMS at some point many years down the road, would you split the case to replace the seal?

I didn't think so.

Don't confuse a need for the best way to proceed. Of course you wouldn't slit the case on an older/assembled engine but that isn't the best way when you have a choice.
Perhaps if the seal wasn't pounded in after assembly there wouldn't be a need to install a new one. Rear main seal leaks in 911 engine is a relatively rare occurrence probably because engine builders don't pound in the seal in the first place.

[PeteKz]

Henry, fair enough, but don't conflate light tapping with "pounding." That's not a fair description either. Every one of us has installed seals by lightly tapping around the edges, using blocks of wood, or slightly smaller sockets, or some other improvisation; and done so successfully.

Curious, does anyone know how the RMS seal gets installed at the factory?

[Jeff Alton]

Like I said, we install after assembly. 100 or so motors? Not the number that some rebuilders have done on here.

We also replace/install on countless assembled motors that come into our shop where the engine/gearbox our out of the car. We use the correct install tool. Never had a problem in either scenario after 20 plus years.

To each their own. Do what works for you. Much like the sealant thread.

I would be worried about the seal getting cocked one way or the other during assembly and not set to correct depth (how do you measure it accurately while assembling?).

So, everyone do what works for them. We will still never install it during case assembly.

Cheers