In 1973 i owned a 1972 newport coupe with a 400 engine,the performance and fuel mileage was a disappointment . after thinking about my options for improvement i decided to advance the cam 6 degrees.a chevy guy that worked for me warned about the the single bolt and make sure the alignment pin was strong enough. when i said you don't need the PIN ,he got lite headed and bet me the cam gear fall off in 10 miles. i advanced the cam without the pin in place and after 10,000 miles collected the $10 bet. the improvement was 14.5 to 18 mpg, with a few carb changes. i traded the car at 150,000.