Is there a formula for figuring combustion chamber volume?
 

I can't remember ever seeing anything for this

I've got some E7's milled .035,assuming they were 64cc's

before, what would they be now?

Here's something just found on the web for E7TE's.

Cut CC's
OE - - - 64.00cc
.010 - - 62.40cc
.020 - - 60.92cc
.025 - - 60.15cc
.030 - - 59.38cc
.035 - - 58.61cc
.040 - - 57.84cc