Re: Smoking FE390
My first thought would be the valve seals weren't installed properly causing a leak and if you are using facktory seals with double valve springs it could cause the seals not to seat back down as the valve travels up and down.
You might also have an angle problem with your intake meeting up with your heads. I always use a protractor to make sure the angles are exact. If not you'll have leaking. Also if your intake sits up a bit high on the heads it will leak, by way of vacuum sucking oil through the lower end of the intake gasket.
Check the PCV make sure that clean and operating correctly.