I have a 383 builded up and it has 10 5 to 1 comp. Flat tops bored 30 over with a hot cam and it runs fine on 93 octane. It does a little better with a oct booster added.. It dyno at 513 hp and 498 toruqe. It is not a daily driver due to gas mileage and the cam. It is a 41 chevy Hot rod for cruise night. Theres no way you can run 13 to 1 on pump gas and as a daily driver. It would make a good car for the strip but thats about it.And yes speed and hp cost.