Originally Posted by pfarber
Swelling the seals to prevent a leak is a common patch. I'd say that it really doesn't fix anything, as you're still leaking oil.

Depending on the reason for the leak (old seals, a groove worn on the sealing surface etc) swelling of the seals may not do much.

Not sure if a 49 would have the rope seal or newer neoprene type. My 42 was rebuilt with rope seals but that can also affect the swelling action.

I would consider 1qt every 200 miles a serious enough leak to fix ASAP. Seals are like $20 and doing the front and rear seals on a 216 is something you can do without taking the motor out. Your driveway must look like a BP oil spill.
Stovebolt gaskets were mostly cork and the seals were either rope or leather. ALL of these are designed to utilize oil as a sealing agent by swelling the materials to provide the seal. A common mistake made when using cork gaskets is using a RTV on both sides of the gasket, preventing oil from making its way into the cork. Having said all of that, the OP may be a bit optimistic in hoping to solve such severe leakage with a bottle of something.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission