ive got a 71 402/396 300hp its 8.5:1 comp. if i use a set of 69 closed chamber heads will the compression go up and if it will how much thanks

Yes it will go up, but that depends on what pistons you have. If you think you're really at 8.5:1 with open chamber heads, ther closed chambers should put you around 9.25 to 9.5:1.

There are many things that come into determing REAL final compression ratio:

Piston
Deck Height - Is the block decked?
Combustion chamber size - heads milled?

You should get an advertised 10.25, but this was usually wrong, down to 9.5 or so.