Chambers are 68cc. I was surprised cranking PSI is only 180. My guy says it's due to the pretty big overlap in the cam.
My cranking PSI in the motor i've been running for 2 summers is 195. It's a 10.75:1, Iron heads(Indy/RHS). Just yanked it out yesterday. Felt kinda weird pulling out such a great running motor, but 45 more horses and 60 pounds off the front end should be worth it. Those Indy heads are 63 pounds a piece! I weighed 'em!
Might put that engine in the classifieds, might keep it for back up........not sure yet.