No that is not normal. You could have a blown head gasket or a cracked head. I'd do a compression test on all of the cylinders.

 

have you over-heated lately?
if you did, you might have warped the head

 

i had that happen to me on a moped when i was 16. i was told it was gunk and buildup on pistons and walls... since i kept pedaling to start it, the pistons pushed it out threw the exaust. anyways sounds like old oil and water mixed

 

might have a loose exhaust stud. [really wild guess] Notice any leaking fron the engine?

 

have you checked to see what your plugs look like - look to see if they are wet with gas or antifreeze and what moparguy said isnt all that silly so i would also check that as it will blow into the exh-manifold and i would even look on top in the rad to see if you have any oil floters