Rear Main Seal Replacement

[BigNate]

Well - I got my jalopy running again after 10+ years.   Within a couple of miles it developed a rear-main leak (well down the back of the block - so I assume) and by the time I got it home it is almost a stream (drops every inch or so as I pulled it up the driveway). 

So - a couple of questions...
1) This is a 352 in a '65 custom - do I pull the engine or try to do this while it is in the car? I understand that it "can" be done either way - but I'm not interested in trying to do it in the car if doing so means being a contortionist.
2) Napa has 2 piece replacement seals - do I try to find an old rope type replacement or just go with the new style - or does it depend on what I find when I get the cap off? 
3) Any other "gotcha's" about doing this? Other advice?

Thanks...

[fastback 427]

You can buy a cheap borescpe for your phone and try to see where the leak really is. We thought my rear main was leaking years ago, so we pulled it and ran it on the floor. Yeah a little sketchy, but it was a leaking galley plug.

[jayb]

Before you pull the motor, make sure that the leak isn't from the back of the intake manifold.  That is a very common spot...

[wsu0702]

If it is indeed the rear main seal you can easily change it without pulling the engine.  Here is a link to the special tools required.  https://www.amazon.com/Lisle-27000-Sneaky-Pete-Tool/dp/B0002SRCJW

[BigNate]

Thanks all - I'll take a closer look before assuming that it is the main.

[BattlestarGalactic]

I had a galley plug leak in my black car.  Seems it was a straight thread plug instead of tapered.  It was just bottomed in the hole, but not really sealed.   I chased that leak for a few years til I pulled the transmission/flywheel and looked better.  I then spun the oil pump with a drill and watched that plug just seep oil.  Ugh.

[cammerfe]

If it is indeed the rear main seal you can easily change it without pulling the engine.  Here is a link to the special tools required.  https://www.amazon.com/Lisle-27000-Sneaky-Pete-Tool/dp/B0002SRCJW

Long ago when rope seals were common, we found that it was possible to thread a wood screw into one end and pull it out while also turning the crank to provide assistance. Lip seals can be pushed in with thumb pressure---make sure the lip is pointed right---and squirting 'Right Stuff' into the sides will seal them good, too.

KS

[a70eliminator]

My 428 cougar developed a rear main leak, I took the carb off and made a blank off plate with a little 1/4" barb fitting, plugged all the external crankcase openings, dip stick tube, valve cover holes and manifold holes, used a squeeze bulb and by hand pumped a positive pressure into crankcase and could distinctly hear gurgling from the rear main seal, I haven't fixed it yet but hope to do it without pulling the motor, should be easier in a mustang cougar with the removable crossmember under the pan.

[C6AE]

In the early 1960's I learned that changing a "rope seal" in a 352 was pretty much a waste of time unless you changed the main bearings and used the .001-.002  undersize, on at least the lower ones.
 I have seen more than one cam plug installed backwards that was pushed out (gone) and leaked a steady stream like you describe. (Rear mains on FE's don't usually leak "that much"! I would guess it is something else...)