How many different heads were used on the Honda CB450?

- CB450 K0-K4 (1965-1968): The first CB450 head had round ports and dual overhead cams. It was used on all K0-K4 models.

- CB450 K5-K6 (1969-1970): The second CB450 head had round ports and a single overhead cam. It was used on all K5-K6 models.

- CB450 K7-K8 (1971-1972): The third CB450 head had oval ports and a single overhead cam. It was used on all K7-K8 models.

- CB450 K9-K10 (1973-1974): The fourth CB450 head had square ports and a single overhead cam. It was used on all K9-K10 models.