making an oil tank do I need ta add a vent? for evo engine

 

No vent needed, the engine breathing arrangement will take care of that regardless whether it's a top or bottom breather.

You WILL need to solder a standpipe in each of oil return and crank case/tank vent fittings. Feed comes of the bottom of course but the other 2 must be above the oil line in the tank at all times. Preferably, you'd make a short "L" on each pipe and index each so they do not point at each other. Better yet, so the return points toward the fill and the case/.tank vent is pointing away from fill.

 

Nice to see some fabrication going on around here.

Good looking welds:

 

Every search for "harley evo oil line routing" shows a vent line to the tank. As another poster mentioned, you'll need a dip tube in the supply.

 

You got 3 holes..

1 feed
2 return
3 vent to cam case..

2 and 3 need to feed into the tank above the oil level.

Add:
I would say you also need an oil drain and filler..