86 200x smoking and a lot of pressure in crankcase?

[1972mercury]

I got a 86 200x motor I was rebuilding got it all done ran good but it started smoking but I never replaced the valve seals even thou I should of but now I been hearing a hissing noise and it's coming out the carb then when the engine is off I started to take the the oil cap off theres a lot off pressure in the crank case as you start to unscrew the oil cap I'm not sure if that's normal?

[Dirtcrasher]

That means it's getting past your rings............

[WJG1000W]

or you crank case breather is plugged

[just ben]

or you crank case breather is pluggedthat doesn't explain the smoke.Sounds like blow by

[oscarmayer]

yes it does, if you have too much pressur ein the crank case, it will cause oil to be pushed into the cyclinder when running and cause smoke as well as when turned off, cause the blowby sound.

you coudl haev put the rings in backwards, put them in wrong, broke a oil ring, or have a bad bore to piston side/bore job.

esiest is to check to ensure crank case is not plugged by blowing in the tube that sticks out the top next to the cyclinder where the big hose is at that leads to air. take the oil fill cap out and blow through the hose, if you cna blow fairley easy, it's not plugged, if you cannot it's plugged. take the hose off and try to blow through it, if nothing repale hose, if you can, then try to blow through tube (using another new hose) and see if it is plugged. if plugged, you will have to use a small flat head and gently dig out the crid blockig up the hole till it is cleared. when done, do an oil change and while oil plug is out, take carb cleaner and spray down vent hole to clean out where debres would have dropped.

if that doesn;t work, you have to dissamble the head and top end to see what is going on.

[WJG1000W]

did you try it? any updates