I've had two motors that made close (526 C.I.high compression bracket motor 440 block that made 845 HP on race gas and 518 C.I.,10.78 to 1 comp. ratio 400 block 775 HP on pump gas Both motors where dyno tested on a DTS engine dyno in Klamath Falls, OR which is at 4300 Ft elevation, I don't remebmer the uncorrected numbers now but the pump gas motor ran faster,9.993 at 134.+ MPH through the full 3 inch exhaust on Oregon 91 octane pump swill than my 3450 lb Duster was legal for