ol'merc: 2/12/00 - 9:20:33 PM
merc rear main seal
Is this supposed to happen? Today I installed the new rope seal on my '50 Merc, dropped the crank in,torqued the main bearings, then gave the crank several turns. I went on and installed the timing gears and turned the crank some more. Next, I was surprised to find that the rear main seal (the metal half holding the rope seal that resides in the block) had come out most of the way. I had followed the book instructions and applied orange RTV to the back side of this seal (very thin coat). Looks like tomorrow I'll have to pull the crank, remove the seal entirely (even though I tapped it back into position) and I'm guessing here - secure the metal seal with locktite? I know that after assembly of the oil pan, the pan will hold this seal in place. But it doesn't seem right that the seal should travel like this (too used to building ohv 260,289,302 etc.). Any ideas here? Thank you.

JWL: 2/12/00 - 10:35:45 PM
RE: merc rear main seal
Yep, that can happen with that style block. I like to let the sealant on the seal holder ''set-up'' with the holder in place for a day before inserting the rope. It is also important to soak the rope in oil for a couple of hours before forming it into the holder.

rumble seat: 2/14/00 - 5:20:34 PM
RE: merc rear main seal
ol'merc: I agree with JWL completely. However, I don't use the FH rear seal that comes in the engine gasket set since I've had several leak over the years. I feel these are the old school technolgy and the newer technolgy has made lots of improvements on rope type seals. I started using two front seals made for a 1983 Buick V6 3.8 litre. These are impregnated with graphite and some other stuff and don't seem to leak and don't cause hardly any drag on the crank compared to the FH type... which is nice when you're assembling one. I don't soak them but coat them with assembly lube and install them with some silicon. They're too long and have to be trimmed, but I haven't had one leak in the past 10 years or so. Just my opinion and dumb way of doing things. Incidentally, most engine rebuilders use a lip type seals on these Buick engines and throw the rope seals that come in the gasket set in the trash. They'll usually save them for you and give them to you at no cost you if you ask.

rodnut: 10/28/01
Sam- I'm afraid that you are confined to a rope seal here. Most of the seals that come in the gasket sets are fine AS LONG AS THEY ARE PROPERLY INSTALLED! Here is my method, and I've never had a leaker yet. 1. Soak the seal halves in motor oil overnight. 2. Install the seal into the main cap, and using a tool (I machined a piece of steel bar stock to the diameter of my c/shaft main journal) or you can use the c/shaft by pushing the cap over the seal area on the crank and tapping on the cap with a dead-blow hammer to fully seat and compress the seal. Then, if you can, find a piece of pipe or a socket about the same diameter (not larger) as the c/shaft. Hold it against the seal and with a VERY SHARP knife (I use military field scalpels) or NEW packing knife, carefully trim off the seal ends nice and square to the cap face. Leave each end about 1/32" proud of the cap surface. I also trim a very slight 45 degree edge on three sides of the exposed ends, but NOT the edge that goes against the c/shaft journal. This prevents the seal edges from pushing out and becoming pinched between the cap and block surfaces when installing the main cap. Next, perform the same drill and seat the other seal half into the block seal holder. After seating the holder in the block, trim the seal ends as above. When you do the final assembly of the main caps, place a small dab (you don't want it squishing out onto the c/shaft journal) of Aviation Permatex (non-hardening) on one side (block or cap, not both) of the seal half ends just before you set and torque this cap. If you do this right, she'll be snug as a bug in a rug! The secret is to just take your time. I also use a bit of the Aviation Permatex on the seal holder at the block when installing. Like I said, I've done a lot of these, and it works for me... rodnut

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