Fresh 383 rear main leak during install

Some people install them wrong. They put those side seals in dry with no additional sealant. They are supposed to be dipped in diesel or something, and they swell after being installed. I use Permatex Ultra Seal instead, and clock the seal halves slightly to mis-align with the parting line between the block and the retainer. I also back fill the cavity behind the seal with sealant.