So I have a fully built b16 head and a fully built b20 block, when I start it up
It smokes and it smokes a little bit when I am driving around, is it that the rings need to fully seal, or do I need to do more work? Block has 300 miles on it

 

"Fully built" huh?

Bad headgasket? Bad valve seals? Compression test?

 

Whats fully built? If its a fresh build, it should on a dyno getting abused so the rings will seat right. Driving it around wont much since you cant beat on it.

 

Rods pistons bearings seals cams valves retainers everything everything has been replaced and it was due to having the same problem with my b16 block but the smoke was worse, It smokes one good tine when it starts up avd when it's running there's very little coming our but it still is, what should I do, do I wait x amount of miles for it so the rings ca sit, or do I have my dude take it apart and figure out how to make it stop

 

hate to break it to ya dude but your rings arent gonna seat properly if they havent already

80% of the ring seating occurs within the first 20 miles.

 

What tune is on the ECU?
You could just be very rich.
Is it using oil?
Any changes to fuel system?

I've also seen engines in which the ring gaps were not oriented properly around the piston when it went into the block smoke like that.