Need help figuring out my dynamic compression.

bignick said
My engine is a 340 based 4.100" bore, 4.00" stroke. Heads are 63cc, piston is at 0.00 deck height , head gasket is 0.051" compressed thickness with a 4.180 bore. Cam is a Hughes solid flat tappet 260/264 @0.050

What piston? If it has valve reliefs/dome it will change the compression.

I assume this is the hughes cam you are running? Hughes Engines

EDIT: Also need your altitude.