67-85ish 318 have open chamber untill the roller cam closed chamber 302 headed 318 from what I understand that closed chambers are 60-64cc open chamber are 64-68cc and 340/360 are 68-72cc, I've never measured myself but from what others have said most heads are on the higher side in cc. from what i've read most engine don't come anywhere near the factory CR ratings. the only way to know forsure is to measure