There are a lot of discussions on the side seals that are on each end of the rear main cap, that seal the cap to the block. The discussions are almost always on the 4 cyl Fords. There a few different types. There are what is called paper, which I have never seen, that is supposed to insert easily then seal as oil is absorbed. Then there are the ones that appear to be rubber that you slide down in and then insert a flimsy steel pin into in order to tighten it. The problem with these is even with profuse lubricating the rod bends when you have it 3/4 of the way in. These, in my opinion are just plain miserable. HoboNC recommended the Victor-Reinze RTV silicone applied into the space. I have done this and it worked well with the first and second one, but the third leaked, and after taking it apart again the problem was that there was an air gap in the sealant. The engine that I did most recently was an old Nissan. The seal that I got from a specialty vendor included some very nice side seals They are molded of rubber that is stiff enough to slide in easily, yet soft enough to make a good seal. The big thing is that they have a a rod molded inside that protrudes just slightly at one end. They work extremely well! It would be great to know who makes them and see if they are available for other applications. One would think that they would be. The vendor in CA that I got them from guards most of his sources very jealously, repacking them to eliminate the manufacturer's identity. Hs anyone come across seals like this?

Paper side seals coat with good RTV never depend on oil to seal them

Rubber with the pin YES a P.I.T.A. I still coat them with good RTV

Victor-Reinze RTV leave the bearing cap a little loose inject the RTV this leave a space between the cap and block for the air to be pushed out are probe/pack with a coat hanger.

Nissan seal sounds more like the paper I would treat the same with good RTV. Paper works good I don't depend on the oil to complete the seal...

On all check for leaks before you button the pan on I hope you have the engine on a stand leak check with low compressed air and a soap solution by applying air to the inside and soaping the outside.

All will BITE : ( I have had to keep at it mutable times to get a seal while the engine was on a stand. With the engine buttoned up block off all vents to the crank case apply low pressure air 1/2 to 2 lbs and soap the rear seal and all gaskets/seals this is the time to find the leak... This also works on the intake, fuel and cooling system...

If you can get your hands on one of these life will be good... I use a Red Line machine its saved my bacon and paid for its self several times over...



https://www.youtube.com/watch?v=IbdQH5_sMOA

Seems like a fel-pro or victor gskt set got for Y block or 134/172 had them. Last one had the grooved with pin. The manifold side was pita other wasn't as bad of course it was a in frame.

What I do is pack the side seal cavity with cotton string and a little RTV. Tap it in with a wee punch. Take a bit of time but it does not leak as far as I can tell.