Leaks with the engine stopped or leaks all the time?
Pre-Mono's need the juice turning off when parked up as they tend to leak, although leaking isn't usually a problem with the engine running.
Except when leaking on a running magneto
G'day Gordon.
I gave up on trying to seal my 276 about 40 years ago
and fitted a concentric. No internet back then to help.
Do a search, there's lots of info on them now.
Cheers