Lycoming service instruction 1125C covers the approved sealants and methods for sealing the crankcase halves.
http://www.lycoming.com/support/publ...fs/SI1125C.pdf
SI 1125C calls out "POB #4 Perfect Seal" sealing compound as one of the approved sealants. I couldn't locate any of this sealant. So I called the company which is now just called Perfect Seal. They bought POB. POB stood for "Post Office Box" ! They had trouble coming up with a name
Perfect Seal's phone number is 513-542-8444. Talk to Dave if you have any questions.
The #4 perfect seal is sold by NAPA auto parts under the Victor Reinz label.
Napa part # JV66B. My local store had to order it.
