318 compression ratio

In that case, exit feeble mind for one that works.

After you cc the head, measure how far down the hold the piston is, if the piston has valve reliefs, cc them, find out head gasket thickness and bore.
Come back with these values and I (we'll) add in the bnore and stroke of the engine to find out what the ratio is.

OH! Is this engine overbored? Let us know.