One trick I like to use is to form the block half of the gasket in the cap, then when you go to install it, it fits much easier around the crank and it should drop into place. Just don't trim the ends till its up in the block. You will need to form it a couple of times to get at least one end and enough to go around half the crank.
Take the time to order a seal from Best, nothing else will seal like they do, or I should say no other rope type material will seal like they do.
