I helped a friend of mine replace a rear seal and pan gasket on his spare 216. Now that motor was on an engine stand with no transmission to hold things in place. The following is for the woven rear seal material.
We loosened all of the main bearing bolts and removed the last main bearing cap and lift the crank off the bearings. Now the seal is stuck in the grove and it must first be loosened. I pushed small stiff wire (old chock cable) between the seal and the block do this several times from both ends and try to make several new paths. The wire should be long enough to stick out past the block 3-4 inches. With two vicegrips, grab the wire ends and lift the seal out of it's grove in the block, thus breaking it's adhesion to the seal grove. Now with some help from someone, turn the crank and at the same time rotating the seal out. Check as best as you can to make sure that no old seal material was left behind.
With your new tool, install the new seal, again rotating the crank, some oil on the new seal may also help. Retorque the 3 crank cap bolts. The new seal should stand proud of the block and the last bearing cap. This is where we get into 2 schools of thought, 1- trim, 2- leave it as is. This all depends on how long the seal ends are? I like to see the ends stand proud 1/16" to 1/8" at all 4 ends. Install the last bearing cap and torque, remove the rearing again and inspect. Your looking for seal material squeezed between the bearing cap and the block, this MUST be removed, if not it will change the oil clearance between the bearing and crank. Wipe off any oil with alcohol and use a sealer (not much) at the seal area (on the cap).
Personal note, I used Permatex Aviation, I don't like Silicone in oil environment, oil will sep between Silicone and steel.
"Silicone has it's place, but every place"
Woodildo
