273 head modding

1.78/1.50-inch , You can put bigger valves in i.e 2.02-inch intake valves , but they will be shrouded by the small cylinders and wont do you any good. A good set of 302 casting swirl port heads from a mid 80s 318 will go on and flow well but depending on the year of your cylinder heads you may need to swap your intake.