Can some one tell me what the compression ratio would be on a stock bottom end LS1 with a 64cc head and a 0.40 cosmic head gasket?

 

From the post linked below I see Tony Mamo from AFR stating that 63cc with 0.040" gasket is 11.0:1 SCR... so with a 64cc chamber I estimate that you would be right around 10.75:1 SCR...

https://ls1tech.com/forums/generatio...rations-3.html

Or you could try googling for a compression calculator if you're still curious.

 

According to the compression calculator I use you would be at 10.86:1.