Hey guys: Building,(assembling) a 390 for my bumside and the rear main side seals are collapsing about 1/4 in below the bearing cap when I drive the nails in. So I'm giving some serious thought to using the packed string method. Have any of you tried that? I'd like to hear your experences with that method.
Also I was wondering about running a thin bead of silicone down the cap from the inside it would be aeasy to do but I don't know if the stuff will hold up inside the crank case,hot oil and such.

 

I have a bumpside with a 390, but never tried that. I'd say Tigerdan is one of the best FE engine guys in this chapter. Maybe he will know something. Otherwise you may want to check the FE engine forum as well. Here is the link.

 

When I did the 428 in my wifes T-Bird I had some problem at first with them as well. What I did was as I installed the bearing cap I appied a little slicone to the grooves. The put a little on the side seal like a lubicant and slid them in. You'll want to move fast. they stuck out about a 1/4". then drove the nails in. When I was done everthing was flush. I've never had a leak.

 

Make sure that the seals are bone dry when you go to put them in. If you get any oil on them they swell up and it'll be very difficult to install them.

The nails are installed in the narrow side of the seal facing inward.
Sharpen the nails to a point and install point down. Insert the seal halfway into the main cap grove, then install the main cap and seal together, (along with the crank seal of course) slowly pushing down the seal and nail as the main cap bottoms out. Then soak the seal with WD40 or some other very light lubricant to make it swell and tighten. You get one shot at it, because you'll most likely ruin the seals if you take the cap back off, especially after it swells.

You should also offset the rear main seal halves about 1/8" or so to help them seal better.