Ok ..I was hunting for non polarized caps and I see you can make them....
If take two caps 4uf and 4uf both at 450v (equals 8uf at 450V right?) hook up - ends together...do I then connect two + ends to circut? Because I thought that if I just hook up two 4uf at 450V + to + - to - I will get 8uf at 450V....Help me I am confused

You got that bass-akwards.

If you take two regular polarized electrolytic caps 8uf @450v and connect them in SERIES back to back
( minus to minus) or (plus to plus)
will give you HALF the capacitance and twice the voltage rating.

So you will get a 4uf 900vdc ..NON polarized cap.
But if you use it in AC you will have to de-rate the voltage down to about 40% of the 900vDC = 540-vAC

My math error:
40% of 900 is 360vAC

Ok THANK YOU
:
:If you take two regular polarized electrolytic caps 8uf @450v and connect them in SERIES back to back
: ( minus to minus) or (plus to plus)
:will give you HALF the capacitance and twice the voltage rating.
:
:So you will get a 4uf 900vdc ..NON polarized cap.
:But if you use it in AC you will have to de-rate the voltage down to about 40% of the 900vDC = 540-vAC
: