A-H 100 cranks have to be machined to accept a seal, on the 6-cyl cars, the seal is installed aft of the scroll and can be installed in situ. Reported results are mixed, from 'outstanding' to "didn't do a dang thing," probably depending a lot on the correctness of the install. We put one on our BN2 and it still leaks, but I think it's from excessive sump pressure. For my BJ8, my machinist recommended a PCV setup instead, which has reduced but not eliminated oil loss through the bell housing.