Street driven MC powered cars
I run a stock GSXR 1100 (oil cooled) engine in my Sportech. The car and driver weighs about 1300 lbs. I can get about 25 mpg driving relatively sane. I figure the engine makes about 150hp. I think you'll be hard pressed to get 20mpg if you can get the car weight down to 1800 lb. My 67 Cooper S weights 1550# and your Cortina is a lot larger. You should start with something smaller and it will be a lot more fun. Standing starts (stop light racing) will be difficult and hard on the clutch.
Dave
(funcar dot com)